Past Seminars
Tue Sep 29 
Dynamical Systems2:30pm  Via ZoomDynamical Systems Seminar 
Tue Sep 29 
IMA Data Science Lab Seminar1:25pm  OnlineMultiPerspective, Simultaneous Embedding and Theoretically Guaranteed Projected Power Method for the Multiway Matching Problem Vahan Huroyan, University of Arizona Abstract:We address two important subproblems of Structure from Motion Problem. The first subproblem is known as Multiway Matching, where the input includes multiple sets, with the same number of objects and noisy measurements of fixed onetoone correspondence maps between the objects of each pair of sets. Given only noisy measurements of the mutual correspondences, the Multiway Matching problem asks to recover the correspondence maps between pairs of them. The desired output includes the original fixed correspondence maps between all pairs of sets. The second subproblem is called MultiPerspective Simultaneous Embedding (MPSE). The input for MPSE assumes a set of pairwise distance matrices defined on the same set of objects and possibly along with the same number of projection operators. MPSE embeds points in 3D so that the pairwise distances are preserved under the corresponding projections. Our proposed algorithm for Multiway Matching problem iteratively solves the associated nonconvex optimization problem. We prove that for a specific noise model, if the initial point of our proposed iterative algorithm is good enough, the algorithm linearly converges to the unique solution. Numerical experiments demonstrate that our method is much faster and more accurate than the stateoftheart methods. For MPSE, we propose a heuristic algorithm and provide an extensive quantitative evaluation with datasets of different sizes, as well as several examples that illustrate the quality of the resulting solutions. I received my PhD in mathematics from the University of Minnesota in 2018, under the supervision of my advisor Prof. Gilad Lerman. Since 2018, I've been working as a Postdoctoral Research Associate at the Department of Mathematics of the University of Arizona.

Tue Sep 29 
Climate Seminar11:15am  ZoomClimate Seminar TBA 
Mon Sep 28 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 28 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Sep 28 
Special Events and Seminars11:00am  https://umn.zoom.us/j/96572145611HAGMTPDE Seminar Hyunwoo Kwon, Republic of Korea Air Force Academy, South Korea 
Fri Sep 25 
MCFAM Seminar7:30pm  https://umn.zoom.us/j/99433158383?pwd=T3h6LzlTWCActuarial Implications of COVID19 Max Rudolph, Rudolph Financial Abstract:COVID19 has had a material impact on all practice areas of the actuarial profession, ranging widely include traditional areas like health and mortality claims, assets and economic activity, but also risk management and strategic planning. This session assumes you know many of the basic statistics and provides observations about how analysis of the virus is evolving.Bio: MAX J. RUDOLPH, FSA CFA CERA MAAAMax Rudolph is a credentialed actuary, active in the AssetLiability Management and Enterprise Risk Management space for many years. He was named a thought leader in ERM within the actuarial profession, chaired the ERM Symposium, the SOA Investment Section Council and the SOAs Investment Actuary Symposium. He is a past SOA board member and received a Presidential Award for his role developing the CERA credential. He was the subject matter expert for the original Investment and ERM modules, wrote the ERM courseware document and has been involved with the actuarial professions climate change and pandemic efforts. He is a frequent speaker at actuarial seminars and universities, and an awardwinning author.For the past 14 years Max has led Rudolph Financial Consulting, LLC, an independent consulting practice, focusing its insurance practice on ERM and ALM consulting. He has completed projects relating to life, health, annuity, and casualty insurers. He is an adjunct professor for Creighton Universitys Heider School of Business, where he focuses on ERM and investment topics.Max has completed a number of well received research reports covering topics such as emerging risks, low growth, low interest rates, investments, systemic risk and ERM. Other topics he has written about include pandemics, ALM and value investing. Many of his papers can be found at www.rudolphfinancial.com. He comments on a variety of risk topics from @maxrudolph on twitter. 
Fri Sep 25 
Combinatorics Seminar3:35pm  Zoom ID is 94127949847On a RankUnimodality Conjecture of MorierGenoud and Ovsienko Bruce Sagan, Michigan State University Abstract:Let $\alpha=(a,b,\ldots)$ be a composition. Consider the associated poset $F(\alpha)$, called a fence, whose covering relations are $$x_1\lhd x_2 \lhd \ldots\lhd x_{a+1}\rhd x_{a+2}\rhd \ldots\rhd x_{a+b+1}\lhd x_{a+b+2}\lhd \ldots\.$$ We study the associated distributive lattice $L(\alpha)$ consisting of all lower order ideals of $F(\alpha)$. These lattices are important in the theory of cluster algebras and their rank generating functions can be used to define $q$analogues of rational numbers. In particular, we make progress on a recent conjecture of MorierGenoud and Ovsienko that $L(\alpha)$ is rank unimodal. We show that if one of the parts of $\alpha$ is greater than the sum of the others, then the conjecture is true. We conjecture that $L(\alpha)$ enjoys the stronger properties of having a nested chain decomposition and having a rank sequence which is either top or bottom interlacing, the latter being a recently defined property of sequences. We verify that these properties hold for compositions with at most three parts and for what we call $d$divided posets, generalizing work of Claussen and simplifying a construction of Gansner. This is joint work with Thomas McConville and Clifford Smyth.See seminar website for password: http://wwwusers.math.umn.edu/~ovenh001/seminar.html 
Fri Sep 25 
IMA/MCIM Industrial Problems Seminar1:25pm  ZoomThe Technical and Organizational Challenges of Data Science Catherine (Katy) Micek, 3M Abstract:In October 2012 – shortly after I began my career in the data science space – the Harvard Business Review published the article “Data Scientist: The Sexiest Job of the 21st Century” and generated an enormous amount of buzz about the field. Since then, data science has matured: technical skill sets required to do the work are better defined and specializations are emerging. However, the field is still evolving and how data science is used by an organization can vary greatly. In such a dynamic and broadly defined field, it has been my experience that data scientists need to have a wide range of technical skills augmented by soft skills in order to be successful. In this talk, I will share my experience working as a predictive modeler, data scientist, and software developer across various industries (insurance, energy, and within 3M), as well as provide examples of challenges I’ve encountered as a data scientist. I will also discuss my work on a Digital Solutions Implementation for 3M’s Knoxville plant, a project where we are exploring how data science to understand and reduce product variability for Acrylic Foam Tape. Catherine (Katy) Micek is a Data Scientist at 3M in St. Paul, Minnesota. She holds a Ph.D. in Applied Mathematics from the University of Minnesota. In her Ph.D. thesis, Katy developed mathematical models for polymer gel swelling with applications to artificial bone implants and drugdelivery devices. Katy has worked in both academic and industrial positions since earning her degree. In addition to teaching college mathematics, she has worked on crossfunctional business teams as a data scientist, software developer, and predictive modeler teams across diverse industries (insurance, energy, finance, supply chain, and manufacturing). Katy is also an active speaker and mentor. She is frequently invited to college, universities, and conferences to discuss her technical work and career experiences in data science, and she is a contributor to publications by the Society of Industrial and Applied Mathematics on industrial career options. In her free time, Katy enjoys spending time with friends and family, as well as ballroom dancing, rock climbing, and cooking. 
Thu Sep 24 
Colloquium3:30pm  Zoom ID 91514486597 (contact faculty for pw)Random walks in graphbased learning Jeff Calder, University of Minnesota, Twin Cities Abstract:I will discuss several applications of random walks to graphbased learning, both for theoretical analysis and algorithm development. Graphbased learning is a field within machine learning that uses similarities between datapoints to create efficient representations of highdimensional data for tasks like semisupervised classification, clustering and dimension reduction. Our first application will be to use the random walk interpretation of the graph Laplacian to characterize the lowest label rate at which Laplacian regularized semisupervised learning is wellposed. Second, we will show how analysis via random walks leads to a new algorithm that we call Poisson learning for semisupervised learning at very low label rates. Finally, we will show how stochastic coupling of random walks can be used to prove Lipschitz estimates for graph Laplacian eigenfunctions on random geometric graphs, leading to new spectral convergence results. This talk will cover joint work with many people, including Brendan Cook (UMN), NicolasGarcia Trillos (WisconsinMadison), Marta Lewicka (Pittsburgh), Dejan Slepcev (CMU), Matthew Thorpe (University Manchester). 
Thu Sep 24 
Climate Seminar11:15am  ZoomClimate Seminar TBA 
Thu Sep 24 
Special Events and Seminars11:00am  https://umn.zoom.us/j/93601442665HAGMTPDE Seminar Bingyang Hu, Purdue University, Indiana 
Wed Sep 23 
Probability Seminar9:00am  Via ZoomForest fire processes and nearcritical percolation with heavytailed impurities Pierre Nolin, City University of Hong Kong Abstract:We discuss models of forest fires (or epidemics): on a given planar lattice, all vertices are initially vacant, and then become occupied at rate 1. If an occupied vertex is hit by lightning, which occurs at a (typically very small) rate, all the vertices connected to it "burn" instantaneously, i.e. they become vacant. We want to analyze the behavior of such processes near and beyond the critical time (the time after which, in the absence of fires, infinite connected components would emerge). We are led to introduce a percolation model where regions ("impurities") are removed from the lattice, in an independent fashion. These impurities are not only microscopic, but also allowed to be mesoscopic. We are interested in whether the connectivity properties of percolation remain of the same order as without impurities, for values of the percolation parameter close to the critical value. This generalizes a celebrated result by Kesten for nearcritical percolation (that can be viewed as critical percolation with singlesite impurities). This talk is based on a joint work with Rob van den Berg (CWI and VU, Amsterdam). 
Tue Sep 22 
Dynamical Systems2:30pm  Zoom  see link belowAnderson localization for disordered trees Selim Sukhtaiev, Auburn University Abstract:In this talk, we will discuss a mathematical treatment of a disordered system modeling localization of quantum waves in random media. We will show that the transport properties of several natural Hamiltonians on metric and discrete trees with random branching numbers are suppressed by disorder. This phenomenon is called Anderson localization. https://umn.zoom.us/meeting/register/tJ0lcCsrjIqHN1xLgljWWlDIYBIUwKwJK 
Tue Sep 22 
IMA Data Science Lab Seminar1:25pm  OnlineMatrix Denoising with Weighted Loss William Leeb, University of Minnesota, Twin Cities Abstract:This talk will describe a new class of methods for estimating a lowrank matrix from a noisy observed matrix, where the error is measured by a type of weighted loss function. Such loss functions arise naturally in a variety of problems, such as submatrix denoising, filtering heteroscedastic noise, and estimation with missing data. We introduce a family of spectral denoisers, which preserve the left and right singular subspaces of the observed matrix. Using new asymptotic results on the spiked covariance model in high dimensions, we derive the optimal spectral denoiser for weighted loss. We demonstrate the behavior of our method through numerical simulations. William Leeb is an Assistant Professor in the School of Mathematics at the University of Minnesota, Twin Cities. He earned his PhD from Yale University in 2015 under the supervision of Ronald Coifman, and from 2015 to 2018 was a postdoc in Amit Singer's research group at Princeton University. William's research is in applied and computational harmonic analysis, statistical signal processing, and machine learning. He is particularly interested in estimation problems with low signaltonoise ratios, high dimensionality, and many nuisance parameters. 
Tue Sep 22 
Climate Seminar11:15am  ZoomClimate Seminar TBA 
Mon Sep 21 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 21 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Sep 18 
Combinatorics Seminar3:35pm  Zoom ID is 94127949847Betti numbers of unordered configuration spaces of a punctured torus Yifeng Huang, University of Michigan Abstract:Let X be a elliptic curve over C with one point removed, and consider the unordered configuration spaces Conf^n(X)={(x_1,...,x_n): x_i\neq x_j for i\neq j} / S_n. We present a rational function in two variables from whose coefficients we can read off the ith Betti numbers of Conf^n(X) for all i and n. The key of the proof is a property called "purity", which was known to Kim for (ordered or unordered) configuration spaces of the complex plane with r >= 0 points removed. We show that the unordered configuration spaces of X also have purity (but with different weights). This is a joint work with G. Cheong. See seminar website for password: http://wwwusers.math.umn.edu/~ovenh001/seminar.html 
Fri Sep 18 
IMA/MCIM Industrial Problems Seminar1:25pm  OnlineSIAM Internship Panel Montie Avery, University of Minnesota, Twin Cities Abstract:The event will have graduate students speaking about their experiences with their internships. The facilitator of the event is Montie Averie. The participants of the Graduate Student Internship Panel will be: Carter Chain (interned at Travelers) Brendan Cook (interned at Target) Ty Frazier (interned at Securian Financial and Lawrence Berkeley national lab) Jacob Hegna (interned at Google) Sarah Milstein (interned at Ayasdi, 3M, IDA, Cargill and Smart Information Flow Technologies (SIFT)) Amber Yuan (interned at Argonne national lab, ExxonMobil and Activision Blizzard). The event is organized by the SIAM Student Chapter at the University of Minnesota. 
Thu Sep 17 
Colloquium3:30pm  Zoom ID 91514486597 (contact faculty for pw)25 years since Fermat's Last Theorem Frank Calegari, University of Chicago Abstract:Wiles's proof of Fermat's Last Theorem was published 25 years ago. Wiles's paper introduced many new ideas and methods which have since shaped the field of algebraic number theory. This colloquium talk intends to give a (biased) tour of these developments, especially with regard to questions that might be of interest to nonspecialists. 
Thu Sep 17 
Climate Seminar11:15am  ZoomClimate Seminar TBA 
Wed Sep 16 
Probability Seminar4:00pm  Via ZoomTail bounds for the averaged empirical distribution on a geodesic in firstpassage percolation WaiKit Lam, UMN Abstract:Consider $\mathbb{Z}^d$ with nearestneighbor edges. In firstpassage percolation, we place i.i.d. nonnegative weights $(t_e)$ on the edges, and study the induced graph metric $T(x,y)$. A geodesic is a minimizing path for this metric. In a joint work with M. Damron, C. Janjigian and X. Shen, we study the empirical distribution on a geodesic $\gamma$ from $0$ to $x$: $\nu^x(B) := (number of edges e in \gamma with t_e \in B) / (number of edges e in \gamma)$. We establish bounds for the averaged empirical distribution $E \nu^x(B)$, particularly showing that if the law of $t_e$ has finite moments of any order strictly larger than 1, then roughly speaking the limiting averaged empirical distribution has all moments. 
Wed Sep 16 
AMS Intro to Research Seminar12:20pm  ZoomVegetation patterns in dryland ecosystems Paul Carter Abstract:In waterlimited regions, competition for water resources results in the formation of vegetation patterns; on sloped terrain, one finds that the vegetation typically aligns in stripes or arcs. The dynamics of these patterns can be modeled by reactiondiffusion PDEs describing the interplay of vegetation and water resources, where sloped terrain is modeled through advection terms representing the downhill flow of water. We focus on one such model in the 'largeadvection' limit, and we prove the existence of traveling planar stripe patterns using analytical and geometric techniques. We also discuss implications for the stability of the resulting patterns, as well as the appearance of curved stripe solutions. 
Tue Sep 15 
Dynamical Systems2:30pm  Zoom  see link belowDynamical systems for metabolic networks Nicola Vassena, Free University Berlin Abstract:In this talk I will give an overview of one approach to the analysis of metabolic networks, using dynamical systems. When considered in applications, one of the main features of these networks is that the interaction functions (reaction rates) are practically unknown. That is, the most reliable data is the structure of network. For this reason, we present here a qualitative approach based on the structure of the network, only, where no quantitative information is needed. In particular, following this approach, we introduce how to address some bifurcation problems and sensitivity analysis. https://umn.zoom.us/meeting/register/tJ0lcCsrjIqHN1xLgljWWlDIYBIUwKwJK 
Tue Sep 15 
Climate Seminar11:15am  ZoomClimate Seminar TBA 
Mon Sep 14 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 14 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Sep 14 
Special Events and Seminars11:00am  https://umn.zoom.us/j/91467804294"Harmonic AnalysisGeometric Measure TheoryPartial Differential Equations Seminar" Bruno Poggi Cevallos, University of Minnesota 
Fri Sep 11 
Combinatorics Seminar3:35pm  Zoom ID is 94127949847Order Polynomial Product Formulas and Poset Dynamics Sam Hopkins Abstract:I'll present a heuristic for finding special families of partially ordered sets. The heuristic says that the posets with order polynomial product formulas are the same as the posets with good dynamical behavior. Here the order polynomial is a certain enumerative invariant of the poset. Meanwhile, the dynamics includes promotion of linear extensions, and rowmotion of order ideals and Ppartitions. This talk includes joint work with Tri Lai, and with Martin Rubey. see seminar website for password: http://wwwusers.math.umn.edu/~ovenh001/seminar.html 
Fri Sep 11 
IMA/MCIM Industrial Problems Seminar1:25pm  ZoomFlying High with Math Sharon Arroyo, Shabnam Khamooshi, The Boeing Company, The Boeing Company Abstract:Sharon and Shabnam are members of Boeing Research & Technology. They partner with business units to develop operations research based solutions and mathematical tools that help Boeing reduce costs, improve products and operations. They have developed operations research and math solutions as well as simulation models for applications across Boeing including supply chain, aircraft delivery, airline scheduling, wind tunnel testing, robot scheduling, logistics, communication networks, sensor fusion, rate analysis, and facility layout design. In this presentation, Sharon and Shabnam will give an overview of some of the projects on which they have worked and will give insights into what it is like to work as a mathematician in industry. Sharon Arroyo Shabnam Khamooshi 
Thu Sep 10 
Colloquium3:30pm  Zoom ID 91514486597 (contact faculty for pw)Kinetic theory of structured populations: demographics, cell size control, and stochastic hierarchies Tom Chou, University of California, Los Angeles Abstract:We will briefly review, through two examples, classic deterministic PDE models of population dynamics structured according to attributes such as age and/or size. First, we describe how the original McKendrick model was used to motivate China's onechild policy, and generalize it to include an imposed, finite interbirth refractory period. We quantify the effectiveness of this softer, staggered birth policy and discuss its predicted effectiveness. We then review sizertimeraddertype models used to quantify proliferating cell populations. Here, blowup in mean cell sizes can arise, which represents a challenging numerical problem. Finally, we extend these classic deterministic models to allow for both demographic and growthrate stochasticity by developing a fully kinetic theory. Marginalization of the full density functions results in a set of coupled kinetic models similar to the BBGKY hierarchy. We map out the different combinations of stochastic descriptions and show how the classic agedependent population models are connected to this hierarchy, the lowest order of which is a master equation for the total stochastic population. Differences in the stochastic description of birth through budding or splitting are explored. 
Wed Sep 09 
Probability Seminar4:00pm  Via ZoomNUUMN Joint Probability Seminar 
Wed Sep 09 
Special Events and Seminars11:00am  https://umn.zoom.us/j/99821709760Hessian Estimates for the Lagrangian mean curvature equation Arunima Bhattacharya, University of Washington, Washington Abstract:In this talk, we will derive a priori interior Hessian estimates for the Lagrangian mean curvature equation under certain natural restrictions on the Lagrangian phase. As an application, we will use these estimates to solve the Dirichlet problem for the Lagrangian mean curvature equation with continuous boundary data, on a uniformly convex, bounded domain in R^n. 
Tue Sep 08 
Dynamical Systems2:30pm  Via ZoomDynamical Systems Seminar 
Mon Sep 07 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 07 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Aug 31 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Aug 31 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Aug 24 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Aug 24 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Tue Aug 18 
IMA Data Science Lab Seminar1:25pm  ZoomFairness, Accountability, and Transparency: (Counter)Examples from Predictive Models in Criminal Justice Kristian Lum, University of Pennsylvania Abstract:The need for fairness, accountability, and transparency in computer models that make or inform decisions about people has become increasingly clear over the last several years. One application area where these topics are particularly important is criminal justice, as statistical models are being used to make or inform decisions that impact highly consequential decisions those concerning an individuals freedom. In this talk, Ill highlight three threads of my own research into the use of machine learning and a statistical models in criminal justice models that demonstrate the importance of careful attention to fairness, accountability, and transparency. In particular, Ill discuss how predictive policing has the potential to reinforce and amplify unfair policing practices of the past. Ill also discuss some of the ways in which recidivism prediction models can fail to require the accountability and transparency necessary to prevent gaming. Kristian Lum is on the faculty at University of Pennsylvania's School of Engineering and Applied Science and is the former Lead Statistician at the Human Rights Data Analysis Group (HRDAG). Kristians research primarily focuses on examining the uses of machine learning in the criminal justice system, including demonstrating the potential for predictive policing models to reinforce and amplify historical racial biases in law enforcement. She has also served on Research Advisory Councils for the New York Citys Mayors Office of Criminal Justice and Philadelphias First Judicial District tasked with advising on the development of fairer algorithmic pretrial risk assessments. Kristian holds an M.S. and Ph.D. from the Department of Statistical Science at Duke University and a B.A. in Mathematics and Statistics from Rice University. 
Mon Aug 17 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Aug 17 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Aug 10 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Aug 10 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Tue Aug 04 
IMA Data Science Lab Seminar1:25pm  ZoomLecture Anil Vullikanti, University of Virginia 
Tue Aug 04 
IMA Data Science Lab Seminar1:25pm  Lind Hall 305A Network Science Approach for Controlling Epidemic Outbreaks Anil Vullikanti, University of Virginia Abstract:The spread of epidemics is a very complex process, and stochastic diffusion models on networks have been found useful, especially when modeling their spread in large and heterogeneous populations, where individual and community level behaviors need to be represented. A fundamental problem in such models is to understand how to control the spread of an epidemic by interventions such as vaccination (which can be modeled as node removal) and social distancing (which can be modeled as edge removal). A number of heuristics have been studied, such as selecting nodes based on degree and eigenscore. However, rigorous algorithms with approximation guarantees are not well understood, and is the focus of this talk. We will discuss two approaches for epidemic control from a network science perspective. The first involves reducing the spectral radius of the graph, motivated by a characterization that shows that epidemics in some models die out fast if the spectral radius is below a threshold. We discuss algorithms for this problem and its generalizations. The second approach involves stochastic optimization, using a sample average approximation combined with rounding. We show that this approach gives near optimal solutions in practice, and have interesting structural properties, which might be useful Anil Vullikanti is a Professor in the Department. of Computer Science and the Biocomplexity Institute at the University of Virginia. His research interests are in the broad areas of network science, dynamical systems, combinatorial optimization, and distributed computing, and their applications to computational epidemiology and social networks. 
Mon Aug 03 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Aug 03 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Jul 27 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jul 27 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Jul 20 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jul 20 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Jul 13 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jul 13 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Jul 06 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jul 06 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Jun 29 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jun 29 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Tue Jun 23 
IMA Data Science Lab Seminar1:25pm  OnlineComputational Science for COVID19 Pandemic Planning and Response Madhav Marathe, University of Virginia Abstract:The ongoing COVID19 pandemic represents an unprecedented global crisis. In this talk, using COVID19 as an exemplar, Madhav Marathe is the division director of the Networks Simulation 
Mon Jun 22 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jun 22 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Jun 15 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jun 15 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Tue Jun 09 
IMA Data Science Lab Seminar1:25pm  OnlineData and Models for COVID19 DecisionMaking Forrest Crawford, Yale University Abstract:As states begin to reopen, there is an urgent need for 
Mon Jun 08 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jun 08 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Mon Jun 01 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jun 01 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Thu May 28 
Analysis and PDE Working Seminar3:00pm  https://sites.google.com/view/summerseminarAnalysis and PDE Working Seminar Gianmarco Brocchi, University of Birmingham 
Tue May 26 
Analysis and PDE Working Seminar3:35pm  https://sites.google.com/view/summerseminarAnalysis and PDE Working Seminar <b> </b>Lisa Naples , University of Connecticut Abstract:

Mon May 25 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon May 25 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri May 22 
IMA/MCIM Industrial Problems Seminar1:25pm  OnlineAI for COVID19: An Online Virtual Care Approach Xavier Amatriain, Curai Abstract:With half of the worlds population lacking access to healthcare services, and 30% of the adult population in the US having inadequate health insurance coverage to get even basic access to services, it should have been clear that a pandemic like COVID19 would strain the global healthcare system way over its maximum capacity. In this context, many are trying to embrace and encourage the use of telehealth as a way to provide safe and convenient access to care. However, telehealth in itself can not scale to cover all our needs unless we improve scalability and efficiency through AI and automation. In this talk, we will describe how our work on combining latest AI advances with medical experts and online access has the potential to change the landscape in healthcare access and provide 24/7 quality healthcare. Combining areas such as NLP, vision, and automatic diagnosis we can augment and scale doctors. We will describe our work on combining expert systems with deep learning to build stateoftheart medical diagnostic models that are also able to model the unknowns. We will also show our work on using language models for medical Q&A . More importantly, we will describe how those approaches have been used to address the urgent and immediate needs of the current pandemic. Xavier Amatriain is cofounder/CTO of Curai, a startup using AI to scale the worlds best healthcare to every human being. Prior to this, he was VP of Engineering at Quora, and Research/Engineering Director at Netflix, where he led the team building the famous Netflix recommendation algorithms. Before going into leadership positions in industry, Xavier was a researcher in both academia and industry. With over 50 publications in different fields, Xavier is best known for his work on machine learning in general and recommender systems in particular. He has lectured at different universities both in the US and Spain and is frequently invited as a speaker and senior committee member at conferences. 
Thu May 21 
Analysis and PDE Working Seminar3:35pm  https://sites.google.com/view/summerseminarAnalysis and PDE Working Seminar Wenjie Lu, University of Minnesota 
Tue May 19 
IMA Data Science Lab Seminar1:25pm  OnlineTransmission Dynamics of Influenza and SARSCoV2: Environmental Determinants, Inference and Forecast Jeffrey Shaman, Columbia University Abstract:Dynamic models of infectious disease systems are often used to study the epidemiological characteristics of disease outbreaks, the ecological mechanisms and environmental conditions affecting transmission, and the suitability of various mitigation and intervention strategies. In recent years these same models have been employed to generate probabilistic forecasts of infectious disease incidence at the population scale. Here I present research from my own group describing investigation of the environmental determinants of influenza transmissibility and development of model systems and combined modelinference frameworks capable of simulation, inference and forecast of disease outbreaks with a particular focus on influenza and SARSCoV2. 
Mon May 18 
Analysis and PDE Working Seminar3:35pm  https://sites.google.com/view/summerseminarAnalysis and PDE Working Seminar Jack Burkart, Stony Brook University 
Mon May 18 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon May 18 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Tue May 12 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon May 11 
Analysis and PDE Working Seminar3:35pm  https://sites.google.com/view/summerseminarAnalysis and PDE Working Seminar Guillermo Rey, Wing 
Mon May 11 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon May 11 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri May 08 
Combinatorics Seminar3:35pm  the talk will talk place at this Zoom link, atTroupes and Cumulants Colin Defant, Princeton Abstract:Cumulants are the fundamental combinatorial tools used in noncommutative probability theory. Sequences of free cumulants and sequences of classical cumulants are paired with each other via summation formulas involving partition lattices and noncrossing partition lattices. In several cases, a sequence of free cumulants that counts a set of colored binary plane trees happens to correspond, somewhat miraculously, to a sequence of classical cumulants that counts the decreasing labeled versions of the same trees. We will see that this strange phenomenon holds for families of trees that we call troupes, which are defined using two new operations on colored binary plane trees that we call insertion and decomposition. Troupes also provide a broad framework for generalizing several of the results that are known about West's stacksorting map. We will hint at just a couple of the many ways in which the investigation of troupes could be extended further. the talk will talk place at this Zoom link, at 3:35 CDT. 
Fri May 08 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri May 08 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri May 08 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri May 08 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri May 08 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar 
Thu May 07 
Colloquium3:35pm  VinH 16Colloquium Cancelled 
Thu May 07 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu May 07 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Symplectic Topology 
Wed May 06 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Wed May 06 
PDE Seminar3:35pm  Vincent Hall 570 ,PDE Seminar  Cancelled 
Tue May 05 
Colloquium3:30pm  VinH 16Colloquium 
Tue May 05 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue May 05 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue May 05 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Svetlana Lazebnik, University of Illinois at UrbanaChampaign 
Tue May 05 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon May 04 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium Eric Bonnetier, Université Joseph Fourier 
Mon May 04 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon May 04 
Analysis and PDE Working Seminar3:35pm  TBAAnalysis & PDE Working Seminar Ryan Matzke 
Mon May 04 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon May 04 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon May 04 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri May 01 
Combinatorics Seminar3:35pm  Zoom id 391940053Associahedra, Cyclohedra, and inversion of power series Jose Bastidas Abstract:Abstract: Species and Hopf monoids are powerful algebraic tools to study families of combinatorial structures. Aguiar and Ardila introduced the Hopf monoid of generalized permutahedra and realized many combinatorial Hopf monoids as submonoids of generalized permutahedra. They solved the antipode problem for the Hopf monoid of associahedra and explained how the classical Lagrange inversion formula for power series follows from this. In this talk, we bring cyclohedra into the picture. We solve the antipode problem for this new Hopf monoid and use this result to describe inversion in a group of pairs of power series using the face structure of associahedra and cyclohedra. The talk is based on joint work with Marcelo Aguiar (Cornell University). 
Fri May 01 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri May 01 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri May 01 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri May 01 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri May 01 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar TBA 
Thu Apr 30 
Colloquium3:35pm  VinH 16Colloquium Cancelled 
Thu Apr 30 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu Apr 30 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Symplectic Topology 
Wed Apr 29 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Wed Apr 29 
PDE Seminar3:30pm  Vincent Hall 570 ,PDE Seminar  Cancelled 
Tue Apr 28 
Colloquium3:30pm  VinH 16Colloquium 
Tue Apr 28 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Apr 28 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Apr 28 
IMA Data Science Lab Seminar1:25pm  Lind 305Detecting New Signals Under Background Mismodeling Sara Algeri, University of Minnesota, Twin Cities Abstract:When searching for new astrophysical phenomena, uncertainty arising from background mismodeling can dramatically compromise the sensitivity of the experiment under study. Specifically, overestimating the background distribution in the signal region increases the chances of missing new physics. Conversely, underestimating the background outside the signal region leads to an artificially enhanced sensitivity and a higher likelihood of claiming false discoveries. The aim of this work is to provide a unified statistical algorithm to perform modeling, estimation, inference and signal characterization under backgroundmismodeling. The method proposed allows to incorporate the (partial) scientific knowledge available on the background distribution, and provides a dataupdated version of it in a purely nonparametric fashion, without requiring the specification of prior distributions. If a calibration sample or control regions are available, the solution discussed does not require the specification of a model for the signal; however, if the signal distribution is known, it allows to further improve the accuracy of the analysis and to detect additional signals of unexpected new sources. 
Tue Apr 28 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Apr 27 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Apr 27 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Apr 27 
Analysis and PDE Working Seminar3:35pm  Zoom link. https://umn.zoom.us/j/92809219308PDE aspects of the NavierStokes equations Dallas Albritton Abstract:This will be an expository talk on PDE aspects of the NavierStokes equations.Zoom link. https://umn.zoom.us/j/92809219308 
Mon Apr 27 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Apr 27 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Apr 27 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Apr 24 
MCFAM Distinguished Lecture Series5:30pm  VinH 16MCFAM Distinguished Lecture Series  Cancelled 
Fri Apr 24 
Combinatorics Seminar3:35pm  Zoom ID 391940053Coxeter factorizations and the Matrix Tree theorem with generalized JucysMurphy weights Theo Douvropolous Abstract:One of the most far reaching proofs of Cayley's formula, that the number n^{n2} counts trees on n labeled vertices, is via Kirchhoff's Matrix Tree theorem. After Denes, Schaeffer, and many others, there is a wellexploited correspondence between trees and transitive factorizations in the symmetric group; in particular, the number n^{n2} counts shortest factorizations of the long cycle (12..n) in transpositions. Furthermore, Burman and Zvonkine (and independently Alon and Kozma) have given a "highergenus" formula that enumerates arbitrary length factorizations of long cycles, where each transposition (ij) is weighted by its own variable w_ij, and which has a product form involving the eigenvalues of the Laplacian L(K_n) of the complete graph.In joint work with Guillaume Chapuy, we consider a (partial) analog of the weighted Laplacian for complex reflection groups W. The weights are specified via any given flag of parabolic subgroups, generalizing the definition of JucysMurphy elements. We prove a product formula for the enumeration of weighted reflection factorizations of Coxeter elements, that subsumes the ChapuyStump formula and in part the BurmanZvonkine formula. Its proof is based on an interesting fact that relates the exterior powers of the reflection representation with those Wcharacters that are nonzero on the Coxeter class. We present some further applications of these techniques, in particular, a uniform simple(r) way to produce the chain number h^n*n!/W of the noncrossing lattice NC(W). An extended abstract for this work was accepted for FPSAC 2020 and is available at my website (https://www.irif.fr/~douvr001/). 
Fri Apr 24 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Apr 24 
Probability Seminar2:30pm  Vincent Hall 213Rotationally invariant \alphastable stochastic processes with some membranes located on a given surface M. Portenko, Institute of mathematics, Nat. Acad. Sci. Ukraine, Kyiv. Abstract:Two kinds of singular transformations of a rotationally invariant \alphastable process (x(t))_{t \ge 0} in a ddimensional Euclidean space R^d are considered. They are both connected with the notion of a local time on a given surface S in R d for the process (x(t))_{t \ge 0} (it is supposed that \alpha \in (1, 2) and d \ge 2). The first transformation is determined by a given continuous function (p(x))_{x \in S} with nonnegative values and it consists in killing the process (x(t))_{t \ge 0} at a point x \in S with the intensity p(x). This kind of membranes can be called an elastic screen by analogy to that in the theory of diffusion processes. The second transformation is likewise determined by a given function (p(x))_{x \in S} with positive values and its result is the process (x(t))_{t \ge 0} for which any point x \in S is sticky with the intensity r(x). It is shown that each one of these membranes is associated with some initialboundary value problem for a pseudodifferential equation related to the process (x(t))_{t \ge 0}. These facts are established with the help of some generalization of classical theory of singlelayer potentials for situations where, instead of differential, the pseudodifferential equation mentioned above is considered. 
Fri Apr 24 
2:30pm  Walter B28 Unicode test ? 
Fri Apr 24 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Apr 24 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Apr 24 
1:00pm  Walter B28 Django22 Test Abstract:Testing django 2.2 upgrade 
Fri Apr 24 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar TBA 
Thu Apr 23 
Colloquium3:35pm  VinH 16Colloquium Cancelled 
Thu Apr 23 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu Apr 23 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Symplectic Topology 
Wed Apr 22 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Wed Apr 22 
PDE Seminar3:30pm  Vincent Hall 570 ,PDE Seminar  Cancelled 
Tue Apr 21 
Colloquium3:30pm  VinH 16Colloquium 
Tue Apr 21 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Apr 21 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Apr 21 
IMA Data Science Lab Seminar1:25pm  Lind 305LECTURE CANCELED ,  
Tue Apr 21 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Apr 20 
Applied and Computational Math Colloquium3:35pm  Zoom Meeting: https://umn.zoom.us/j/531493431Numerical Methods for the Optimal Transport Problem Brittany Hamfeldt, New Jersey Institute of Technology Abstract:The problem of optimal transportation, which involves finding the most costefficient mapping between two measures, arises in many different applications. However, the numerical solution of this problem remains extremely challenging and standard techniques can fail to compute the correct solution. Recently, several methods have been proposed that obtain the solution by solving the MongeAmpere equation, a fully nonlinear elliptic partial differential equation (PDE), coupled to a nonstandard implicit boundary condition. Unfortunately, standard techniques for analyzing numerical methods for fully nonlinear elliptic equations fail in this setting. We introduce a modified PDE that couples the usual MongeAmpere equation to a HamiltonJacobi equation that restricts the transportation of mass. This leads to a simple framework for guaranteeing that a numerical method will converge to the true solution, which applies to a large class of approximation schemes. We describe some simple examples. A range of challenging computational examples demonstrate the effectiveness of this method, including the recent application of these methods to problems in beam shaping and seismic inversion.https://umn.zoom.us/j/531493431 
Mon Apr 20 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Apr 20 
Analysis and PDE Working Seminar3:35pm  Vincent Hall 6Analysis & PDE Working Seminar Dallas Albritton 
Mon Apr 20 
Analysis and PDE Working Seminar3:35pm  Zoom link. https://umn.zoom.us/j/99241065966Introduction to the Lp theory of stochastic PDEs Timur Yastrzhembskiy Abstract:I will overview the Lptheory of parabolic stochastic partial differential equations (SPDEs) on the whole space developed by N.V. Krylov in the 90s. If time permits, I will discuss the wellposedness of SPDEs driven by spacetime white noise. Such equations are quite popular in the literature. The talk is aimed at people familiar with the theory of PDEs. Little knowledge of probability is assumed.Zoom link. https://umn.zoom.us/j/99241065966 
Mon Apr 20 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Apr 20 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Apr 20 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Apr 17 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar MFM Modeling Workshop Presenations, University of Minnesota 
Fri Apr 17 
Combinatorics Seminar3:35pm  Zoom ID 391940053A combinatorial eexpansion of verticalstrip LLT polynomials Per Alexandersson Abstract:In 2019, D'Adderio proved that if G(x;q) is a verticalstrip LLT polynomial, then G(x;q+1) is positive in the elementary symmetric functions basis. A conjectured formula The problem of finding such an eexpansion is surprisingly similar to the still open problem of ShareshianWachs, regarding the eexpansion of chromatic polynomials associated with unitinterval graphs. We shall discuss this connection as well. 
Fri Apr 17 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Apr 17 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Apr 17 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Apr 17 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Apr 17 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar TBA 
Thu Apr 16 
Colloquium3:35pm  VinH 16Colloquium 
Thu Apr 16 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu Apr 16 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Symplectic Topology 
Wed Apr 15 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Local Densities of Diagonal Integral Ternary Quadratic Forms at Odd Primes Edna Jones, Rutgers University Abstract:We give formulas for local densities of diagonal integral ternary quadratic forms at odd primes. Exponential sums and quadratic Gauss sums are used to obtain these formulas. These formulas (along 
Wed Apr 15 
PDE Seminar3:30pm  Vincent Hall 570 ,PDE Seminar  Cancelled 
Wed Apr 15 
IMA Data Science Lab Seminar10:10am  Lind 305LECTURE CANCELED Andrea Montanari, Stanford University 
Tue Apr 14 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Apr 14 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Apr 14 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Apr 14 
IMA Data Science Lab Seminar1:25pm  Lind 305LECTURE CANCELED ,  
Tue Apr 14 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Apr 13 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium  Cancelled Dio Margetis, Maryland 
Mon Apr 13 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Apr 13 
Analysis and PDE Working Seminar3:35pm  Zoom link. https://umn.zoom.us/j/538855343The boundary value problems in higher codimension Zanbing Dai Abstract:The boundary value problems have been studied for decades. People first studied boundary value problems for the Laplace operator on bounded Lipschitz domains. Using a change of variable argument, we can map Lipschitz domains onto the upper half plane $\mathbb{R}^{d+1}_+$ and converts Laplace operator into a second order elliptic divergence operator, whose coefficient satisfies a certain smoothness condition, the Carleson measure condition. Recently, David, Feneuil and Mayboroda developed an elliptic theory in higher co dimension. They studied a particular degenerate second order elliptic operator $L={\rm div} A\nabla$. Now, the domain we are interested in has more than one nontangential direction. In this talk, I will focus on flat domain $\mathbb{R}^n\setminus \mathbb{R}^d$ and introduce the Dirichlet results, which has been proved recently. Finally, I will introduce my project on the regularity problem in higher codimension. 
Mon Apr 13 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Apr 13 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Apr 13 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Apr 10 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar Cancelled 
Fri Apr 10 
Combinatorics Seminar3:35pm  The talk will take place at https://umn.zoom.us/Combinatorics Seminar Brendon Rhoades, UCSD Abstract:The {\em Vandermonde determinant} is ubiquitous in algebraic combinatorics and representation theory. One application of the Vandermonde is as a generator for a `harmonic' model of the coinvariant ring attached to the symmetric group which eschews the use of  and computational issues involved with  quotient rings. We present an extension of the Vandermonde determinant to {\em superspace} (a symmetric algebra tensor an exterior algebra) and use it to generate a variety of modules including the recently defined `Delta Conjecture coinvariant rings' of HaglundRhoadesShimozono as well as (conjecturally) a trigraded module for the full Delta Conjecture. We use superspace Vandermondes to build bigraded superspace quotients tied to the geometry of {\em spanning configurations} studied by PawlowskiRhoades which satisfy a superspace version of Poincar\'e Duality and (conjecturally) exhibit unimodality properties which suggest a superspace version of Hard Lefschetz. Joint with Andy Wilson. 
Fri Apr 10 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Apr 10 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Apr 10 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Apr 10 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Apr 10 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar TBA 
Thu Apr 09 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Apr 09 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu Apr 09 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Symplectic Topology 
Wed Apr 08 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Wed Apr 08 
PDE Seminar3:35pm  Vincent Hall 570 ,PDE Seminar  Cancelled 
Tue Apr 07 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Apr 07 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Apr 07 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Apr 07 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Apr 06 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Apr 06 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Apr 06 
Analysis and PDE Working Seminar3:35pm  VinH 301Analysis & PDE Working Seminar Timur Yastrzhembskiy 
Mon Apr 06 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Apr 06 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Apr 06 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Apr 03 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar Cancelled 
Fri Apr 03 
Combinatorics Seminar3:35pm  Zoom id 391941053, available by clicking herThe boxball system and cyclindric loop Schur functions Gabe Frieden, UQAM Abstract:The boxball system is a cellular automaton in which a sequence of balls moves along a row of boxes. An interesting feature of this automaton is its soliton behavior: regardless of the initial state, the balls in the system eventually form themselves into connected blocks (solitons) which remain together for the rest of time. In 2014, T. Lam, P. Pylyavskyy, and R. Sakamoto conjectured a formula which describes the solitons resulting from an initial state of the boxball system in terms of the tropicalization of certain polynomials they called cylindric loop Schur functions. In this talk, I will describe the various ingredients of this conjecture and discuss its proof. 
Fri Apr 03 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Apr 03 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Apr 03 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Apr 03 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Apr 03 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar TBA 
Thu Apr 02 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Apr 02 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu Apr 02 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Symplectic Topology 
Wed Apr 01 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Wed Apr 01 
PDE Seminar3:35pm  Vincent Hall 570 ,PDE Seminar  Cancelled 
Tue Mar 31 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Mar 31 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Mar 31 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Mar 31 
IMA Data Science Lab Seminar1:25pm  Lind 305LECTURE CANCELED ,  
Tue Mar 31 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Mar 30 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Mar 30 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Mar 30 
Analysis and PDE Working Seminar3:35pm  Zoom link. https://umn.zoom.us/j/881291791Mathematical foundations of slender body theory Laurel Ohm Abstract:Slender body theory (SBT) facilitates computational simulations of thin filaments in a 3D viscous fluid by approximating the hydrodynamic effect of each fiber as the flow due to a line force density along a 1D curve. Despite the popularity of SBT in computational models, there had been no rigorous analysis of the error in using SBT to approximate the interaction of a thin fiber with fluid. In this talk, we develop a PDE framework for analyzing the error introduced by this approximation. In particular, given a 1D force along the fiber centerline, we define a notion of true solution to the full 3D slender body problem and obtain an error estimate for SBT in terms of the fiber radius. This places slender body theory on firm theoretical footing. We also present similar estimates in case of freeended and rigid filaments. 
Mon Mar 30 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Mar 30 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Mar 30 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Mar 27 
MCFAM Seminar5:30pm  Vincent Hall 16Social Determinants of Health Shae Armstrong, Optum Abstract: 
Fri Mar 27 
MCFAM Seminar5:30pm  Vincent Hall 16No MCFAM Seminar 
Fri Mar 27 
Combinatorics Seminar3:35pm  Via Virtual  ZoomCounting trees and nilpotent endomorphisms Vic Reiner Abstract:A formula of Cayley (1889) says that the number of trees on vertex set [n]:={1,2,...,n} is n^{n2}. Among its many proofs, my favorite is a gorgeous bijection due to Andre Joyal in 1981. One can also view Cayley's formula as asserting that there are n^{n1} vertexrooted trees on [n], or equivalently n^{n1} eventually constant selfmaps on [n]. This talk will review Joyal's proof, and its recent revisitation by Tom Leinster in arXiv:1912.12562. Leinster gives a beautiful qanalogue of the proof, that proves a qanalogous theorem of Fine and Herstein (1958). The latter theorem counts those linear selfmaps of an ndimensional vector space over a finite field F_q which are eventually constant, that is, nilpotent as linear maps. 
Fri Mar 27 
Analysis and PDE Working Seminar3:35pm  Vincent Hall 6Analysis and PDE Working Seminar 
Fri Mar 27 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Mar 27 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Mar 27 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Mar 27 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305CANCELEDThe Technical and Organizational Challenges of Data Science Catherine (Katy) Micek, 3M Abstract:In October 2012 shortly after I began my career in the data science space the Harvard Catherine (Katy) Micek is a Data Scientist at 3M in St. Paul, Minnesota. She holds a Ph.D. 
Fri Mar 27 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Mar 27 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar TBA 
Thu Mar 26 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Mar 26 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu Mar 26 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Symplectic Topology 
Wed Mar 25 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Wed Mar 25 
PDE Seminar3:35pm  Vincent Hall 570 ,PDE Seminar  Cancelled 
Tue Mar 24 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Mar 24 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Mar 24 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Mar 24 
IMA Data Science Lab Seminar1:25pm  Lind 305CANCELEDKernel Approaches in Global Statistical Distances, Local Measure Detection, and Active Learning ,  Abstract:In this talk, we'll discuss the problem of constructing meaningful distances between probability distributions given only finite samples from each distribution. We approach this through the use of dataadaptive and localized kernels, and in a variety of contexts. First, we construct locally adaptive kernels to define fast pairwise distances between distributions, with applications to unsupervised clustering. Then, we construct localized kernels to determine a statistical framework for determining where two distributions differ, with applications to measure detection for generative models. Finally, we'll begin to address the question of measure detection without a priori known labels of which distribution a point came from. This is addressed through active learning, in which one can choose a small number of points at which to query a label. This is ongoing work with Xiuyuan Cheng (Duke) and Hrushikesh Mhaskar (CGU), among others. Alex Cloninger is an Assistant Professor in the Mathematics Department and the Hal?c?o?lu Data Science Institute at UCSD. He received his PhD in Applied Mathematics and Scientific Computation from the University of Maryland in 2014, and was then an NSF Postdoc and Gibbs Assistant Professor of Mathematics at Yale University until 2017, when he joined UCSD. Alex researches problems around the analysis of high dimensional data. He focuses on approaches that model the data as being locally lower dimensional, including data concentrated near manifolds or subspaces. These types of problems arise in a number of scientific disciplines, including imaging, medicine, and artificial intelligence, and the techniques developed relate to a number of machine learning and statistical algorithms, including deep learning, network analysis, and measuring distances between probability distributions. 
Tue Mar 24 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Mar 23 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Mar 23 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Mar 23 
Analysis and PDE Working Seminar3:35pm  Vincent Hall 6Analysis & PDE Working Seminar 
Mon Mar 23 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Mar 23 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Mar 23 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Mar 20 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar  No Seminar 
Fri Mar 20 
Combinatorics Seminar3:35pm  Vincent Hall 570Combinatorics Seminar  Cancelled Gabriel Frieden 
Fri Mar 20 
Analysis and PDE Working Seminar3:35pm  Vincent Hall 6Analysis and PDE Working Seminar 
Fri Mar 20 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Mar 20 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Mar 20 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Mar 20 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305LECTURE CANCELED Julie Thompson, Boston Scientific 
Fri Mar 20 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Mar 20 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar  Cancelled 
Thu Mar 19 
Colloquium3:35pm  Vincent Hall 16Cancelled  Multiscale Geometric Methods for highdimensional data near > lowdimensional sets Colloquium Cancelled 
Thu Mar 19 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Mar 19 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu Mar 19 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Symplectic Topology 
Wed Mar 18 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory  Cancelled Seminar Cancelled 
Wed Mar 18 
PDE Seminar3:35pm  Vincent Hall 570 ,PDE Seminar  Cancelled Seminar Cancelled 
Tue Mar 17 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Mar 17 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Mar 17 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Mar 17 
IMA Data Science Lab Seminar1:25pm  Lind 305CANCELEDLearning and Geometry for Stochastic Dynamical Systems in High Dimensions ,  Abstract:We discuss geometrybased statistical learning techniques for performing model reduction and modeling of certain classes of stochastic highdimensional dynamical systems. We consider two complementary settings. In the first one, we are given long trajectories of a system, e.g. from molecular dynamics, and we estimate, in a robust fashion, an effective number of degrees of freedom of the system, which may vary in the state space of then system, and a local scale where the dynamics is wellapproximated by a reduced dynamics with a small number of degrees of freedom. We then use these ideas to produce an approximation to the generator of the system and obtain, via eigenfunctions of an empirical FokkerPlanck equation (constructed from data), reaction coordinates for the system that capture the large time behavior of the dynamics. We present various examples from molecular dynamics illustrating these ideas. In the second setting we only have access to a (large number of expensive) simulators that can return short paths of the stochastic system, and introduce a statistical learning framework for estimating local approximations to the system, that can be (automatically) pieced together to form a fast global reduced model for the system, called ATLAS. ATLAS is guaranteed to be accurate (in the sense of producing stochastic paths whose distribution is close to that of paths generated by the original system) not only at small time scales, but also at large time scales, under suitable assumptions on the dynamics. We discuss applications to homogenization of rough diffusions in low and high dimensions, as well as relatively simple systems with separations of time scales, and deterministic chaotic systems in highdimensions, that are wellapproximated by effective stochastic diffusionlike equations. 
Tue Mar 17 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Mar 16 
Applied and Computational Math Colloquium3:35pm  TBAApplied and Computational Math Colloquium Mauro Maggioni, Johns Hopkins 
Mon Mar 16 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium  Cancelled Colloquium Cancelled 
Mon Mar 16 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Mar 16 
Analysis and PDE Working Seminar3:35pm  Vincent Hall 6Analysis and PDE Working Seminar  Rescheduled for March 27 
Mon Mar 16 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Mar 16 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Mar 16 
Topology Seminar2:30pm  VinH 364Topology Seminar  TBA Marcy Robertson, University of Melbourne Abstract:TBA 
Mon Mar 16 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Mar 13 
Combinatorics Seminar3:35pm  Vincent Hall 570Combinatorics Seminar No Seminar  Spring Break 
Fri Mar 13 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Mar 13 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Mar 13 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Mar 13 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Mar 13 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar No Seminar 
Thu Mar 12 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Mar 12 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu Mar 12 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Symplectic Topology 
Wed Mar 11 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Tue Mar 10 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Mar 10 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Mar 10 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Mar 10 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Mar 09 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Mar 09 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Mar 09 
Analysis and PDE Working Seminar3:35pm  Vincent Hall 6Analysis & PDE Working Seminar 
Mon Mar 09 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Mar 09 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Mar 09 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Mar 06 
Combinatorics Seminar3:35pm  Vincent Hall 570Grothendieck Polynomials from Chromatic Lattice Models Katy Weber Abstract:The Grothendieck polynomials are simultaneous generalizations of Schubert and Grothendieck polynomials that arise in the study of the connective Ktheory of the flag variety. They can be calculated as a generating function of combinatorial objects known as pipe dreams, as well as recursively via geometricallymotivated divided difference operators. We combine these two points of view by defining a chromatic lattice model whose partition function is a Grothendieck polynomial. This is joint workinprogress with Ben Brubaker, Claire Frechette, Andy Hardt, and Emily Tibor. 
Fri Mar 06 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Mar 06 
Probability Seminar2:30pm  Vincent Hall 213Dynamics of Deep Neural Networks and Neural Tangent Hierarchy Jiaoyang Huang, Institute for Advanced Study Abstract:The evolution of a deep neural network trained by the gradient descent can be described by its neural tangent kernel (NTK) as introduced by Jacot et al., where it was proven that in the infinite width limit the NTK converges to an explicit limiting kernel and it stays constant during training. The NTK was also implicit in many other recent papers. In the overparametrization regime, a fullytrained deep neural network is indeed equivalent to the kernel regression predictor using the limiting NTK. And the gradient descent achieves zero training loss for a deep overparameterized neural network. However, it was observed by Arora et al. that there is a performance gap between the kernel regression using the limiting NTK and the deep neural networks. This performance gap is likely to originate from the change of the NTK along training due to the finite width effect. The change of the NTK along the training is central to describe the generalization features of deep neural networks.In the work, we study the dynamic of the NTK for finite width deep fullyconnected neural networks. We derive an infinite hierarchy of ordinary differential equations, the neural tangent hierarchy (NTH) which captures the gradient descent dynamic of the deep neural network. Moreover, under certain conditions on the neural network width and the data set dimension, we prove that the truncated hierarchy of NTH approximates the dynamic of the NTK up to arbitrary precision. This is a joint work with HorngTzer Yau. 
Fri Mar 06 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Mar 06 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Mar 06 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar No Seminar 
Thu Mar 05 
Colloquium3:35pm  Vincent Hall 16Cluster formation and selfassembly in stratified fluids: a novel mechanism for particulate aggregation Richard McLaughlin, UNC, Chapel HIll Abstract:The experimental and mathematical study of the motion of bodies immersed in fluids with variable concentration fields (e.g. temperature or salinity) is a problem of great interest in many applications, including delivery of chemicals in laminar microchannels, or in the distribution 
Thu Mar 05 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Thu Mar 05 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570An invitation to contact homology Erkao Bao, Scientist at the company Houzz in Palo Alto Abstract:Contact homology is an invariant of the contact structure, which is an odddimensional counterpart of a symplectic structure. It was proposed by Eliashberg, Givental and Hofer in 2000. The application of contact homology and its variants include distinguishing contact structures, knot invariants, the Weinstein conjecture and generalization, and calculating GromovWitten invariants. In this talk, I will start with the notion of contact structures, then give a heuristic definition of the contact homology as an infinite dimensional Morse homology, and finally explain the major difficulties to make the definition rigorous. This is a joint work with Ko Honda. 
Wed Mar 04 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Tue Mar 03 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Mar 03 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Mar 03 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Mar 03 
IMA Data Science Lab Seminar1:25pm  Lind 305Living 3D World Models Leveraging Crowd Sourced Data JanMichael Frahm, Facebook Abstract:Crowd sourced imagery (images and video) is the richest data source available for 3D reconstruction of the world. The tremendous amounts of available imagery provided by photo/video sharing web sites, not only covers the worlds appearance, but also reflects the temporal evolution of the world, and its dynamic parts. It has long been a goal of computer vision to obtain life like virtual models from such rich imagery. The major current research challenges are the scale of the data, e.g. the Yahoo 100 millionimage dataset (only presents a small fraction of what is needed to model our world), the diversity of data modalities (e.g. crowdsourced photos or satellite images), the robustness, the completeness of the registration, and the lack of data for dynamic elements. Specifically, we are currently facing significant challenges to process Internet scale crowd sourced imagery within a reasonable time frame given limited compute resources. This is particularly true as we move toward automatically creating content for virtual and augmented reality. The talk discusses the UNC groups work on highly efficient image registration for the reconstruction of static 3D models from worldscale photo collections on a single PC in the span of six days, as well as the groups related work on imagebased search to address the scalability. It will also discuss the efforts to overcome the challenges achieving registration completeness and robustness. Additionally, the groups work towards overcoming the lack of observations for the reconstruction of scene dynamics will be presented. This includes for example, reconstructing people and fountains, using crowdsourced Flickr imagery and videos to achieve the goal of bringing the 3D models to life will be presented. JanMichael Frahm is a research scientist manager at Facebook and a full professor at the University of North Carolina at Chapel Hill where he heads the 3D computer vision group. He received his Dr.Ing. in computer vision in 2005 from the ChristianAlbrechts University of Kiel, Germany. His dissertation, Camera SelfCalibration with Known Camera Orientation received the prize for the best Ph.D. dissertation of the year in CAUs College of Engineering. His Diploma in Computer Science is from the University of Lübeck. His research interests include a variety of topics on the intersection of computer vision, computer graphics, AR & VR, and robotics. He has over 100 peerreviewed publications, is a program chair f 
Tue Mar 03 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Mar 02 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Mar 02 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Equilibration of aggregationdiffusion equations with weak interaction forces Ruiwen Shu, University of Maryland Abstract:I will talk about the large time behavior of aggregationdiffusion equations. For one spatial dimension with certain assumptions on the interaction potential, the diffusion index $m$, and the initial data, we prove the convergence to the unique steady state as time goes to infinity (equilibration), with an explicit algebraic rate. The proof is based on a uniformintime bound on the first moment of the density distribution, combined with an energy dissipation rate estimate. This is the first result on the equilibration of aggregationdiffusion equations for a general class of weakly confining potentials $W(r)$: those satisfying $\lim_{r\rightarrow\infty}W(r)<\infty$. 
Mon Mar 02 
Analysis and PDE Working Seminar3:35pm  Vincent Hall 6Analysis & PDE Working Seminar 
Mon Mar 02 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Mar 02 
Student Number Theory Seminar3:25pm  Vincent Hall 570The Satake equivalence II: The geometric formulation John O'Brien Abstract:We continue our discussion of the Satake equivalence and Langlands dual groups with an introduction to the geometric Satake equivalence. The classical Satake isomorphism establishes an algebra isomorphism between the spherical Hecke algebra of one group G and the Grothendieck group of the category of representations of the dual. We wish for a stronger statementan equivalence of categories between a categorical analogue of the spherical Hecke algebra of G and the category of representations of the dual of G. The geometric Satake isomorphism establishes this equivalence, using the geometry of the affine Grassmannian of G to construct a suitable "spherical Hecke category" of G. In this talk, we discuss the affine Grassmannian and introduce the tools needed to understand the geometric Satake equivalence. 
Mon Mar 02 
Topology Seminar2:30pm  VinH 364Topology Seminar  TBA George Shabat, Russian State University for the Humanities Abstract:TBA 
Mon Mar 02 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Feb 28 
MCFAM Seminar5:30pm  Vincent Hall 16Environmental, Social and Governance (ESG) in Finance Through the Lens of a Quant Michael (Zicong) Zhang, Bloomberg LP Abstract:If you can't measure it, you can't manage it  Using math tricks in measuring ESG performance. 
Fri Feb 28 
Combinatorics Seminar3:35pm  Vincent Hall 570Generalized snake graphs from orbifolds Elizabeth Kelley Abstract:Cluster algebras, as originally defined by Fomin and Zelevinsky, are characterized by binomial exchange relations. A natural generalization of cluster algebras, due to Chekhov and Shapiro, allows the exchange relations to have arbitrarily many terms. A subset of these generalized cluster algebras can be associated with triangulations of orbifolds, analogous to the subset of ordinary cluster algebras associated with triangulated surfaces. We generalize MusikerSchifflerWilliams snake graph construction for this subset of generalized cluster algebras, yielding explicit combinatorial formulas for the cluster variables. We then show that our construction can be extended to give expansions for generalized arcs on triangulated orbifolds. This is joint work with Esther Banaian. 
Fri Feb 28 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Feb 28 
Probability Seminar2:30pm  Vincent Hall 213Complexity of high dimensional Gaussian random fields with isotropic increments Qiang Zeng, CUNY Abstract:The number of critical points (on the exponential scale) of a random function is a basic question and is commonly called complexity. The notion of locally isotropic random fields (a.k.a. random fields with isotropic increments) was introduced by Kolmogorov in the 1940s. Gaussian random fields on Ndimensional Euclidean spaces with isotropic increments were classified as isotropic case and nonisotropic case by Yaglom in the 1950s. In 2004, Fyodorov computed the large N limit (on the exponential scale) of expected number of critical points for isotropic Gaussian random fields. However, many natural models are not isotropic and only have isotropic increments, which creates new difficulty in understanding the complexity. In this talk, I will present some results on the large N behavior of complexity of nonisotropic Gaussian random fields with isotropic increments. Connection to random matrices will be explained. This talk is based on joint work with Antonio Auffinger (Northwestern University). 
Fri Feb 28 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Feb 28 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Some Characteristics of Research in Finance Onur Ozyesil, Helm.ai Abstract:The talk will provide a "naive" depiction of general characteristics of research in finance, together with an attempt to classify various research problems/styles present, in order to give a rough understanding of the landscape of mathematical research in finance. Two examples of research problems will also be discussed to provide a more concrete picture of research problems of interest in the industry. 
Fri Feb 28 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Feb 28 
Commutative Algebra Seminar12:20pm  Vincent Hall 213$\tau$Factorization and $\tau$Elasticity Bethany Kubik, University of Minnesota, Duluth Abstract:A more generalized form of factorization, called $\tau$factorization, was introduced in 2011 by D.D. Anderson and J. Reinkoester. In $\tau$factorization, all factors of a factorization must belong to the same equivalence class modulo a fixed ideal. We discuss $\tau$factorization in small settings and $\tau$elasticity in a more general setting. 
Thu Feb 27 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Feb 27 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Wed Feb 26 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Wed Feb 26 
Analysis and PDE Working Seminar3:35pm  Vincent Hall 570Local stability of the critical FisherKPP front via resolvent expansions near the essential spectrum Montie Avery Abstract:We revisit the stability of the critical front in the FisherKPP equation, which travels with the linear spreading speed c = 2. We recover a celebrated result of Gallay with a new method, establishing stability of the critical front with optimal decay rate t^(3/2) as well as an asymptotic description of the perturbation of the front. Our approach is based on studying detailed regularity properties of the resolvent for this problem in algebraically weighted spaces near the branch point in the absolute spectrum, and renders the nonlinear analysis much simpler. We briefly further explore the relationship between the localization of perturbations and their decay rate. 
Tue Feb 25 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Feb 25 
Colloquium2:30pm  Vincent Hall 16Colloquium 
Tue Feb 25 
Dynamical Systems2:30pm  Vincent Hall 213Hyperbolic scattering in the Nbody problem Rick Moeckel, University of Minnesota Abstract:It is a classical result that in the Nbody problem with positive energy, all solutions are unbounded in both forward and backward time. If all of the mutual distances between the particles tend to infinity with nonzero speed, the solution in called purely hyperbolic. In this case there is a welldefined asymptotic shape of the configuration of N points. We consider the scattering problem for solutions which are purely hyperbolic in both forward and backward time: given an initial shape at time minus infinity, which final shapes at time plus infinity can be reached via purely hyperbolic motions ? I will describe some recent work on this problem using a variation on McGehee's blowup technique. After a change of coordinates and timescale we obtain a welldefined limiting flow at infinity and use it to get Chazytype asymptotic estimates on the positions of the bodies and to study scattering solutions near infinity. This is joint work with G. Yu, R. Montgomery and N. Duignan. 
Tue Feb 25 
IMA Data Science Lab Seminar1:25pm  Lind 305Making Small Spaces Feel Large: Practical Illusions in Virtual Reality Evan Rosenberg, University of Minnesota, Twin Cities Abstract:Over the next decade, immersive technologies have the potential to revolutionize how people communicate over distance, how they learn, train, and operate in challenging physical environments, and how they visualize, understand, and make decisions based on an evergrowing landscape of complex data. However, despite rapid technical advances over the past few years and no small amount of media hype, there are numerous theoretical and practical problems yet to be solved before virtual reality can catch up with our imaginations and make good on these promises. Locomotion is one of the most significant interaction challenges because body movement is constrained by the real world. When walking in VR, users may collide with walls or physical obstacles if they attempt to travel outside the boundaries of a "roomscale" space. In this talk, I will present a series of illusory techniques that can overcome these movement limitations by imperceptibly manipulating the laws of physics. This approach, known as redirected walking, has stunning potential to fool the senses. Through a series of formal studies, users have been convinced that were walking along a straight path while actually traveling in a circle, or that they were exploring impossibly large virtual environments within the footprint of a single realworld room. Additionally, I will discuss technical challenges for redirected walking systems and present novel algorithms that can automatically redirect users in complex physical spaces with obstacles. Evan Suma Rosenberg is an Assistant Professor in the Department of Computer Science and Engineering at the University of Minnesota. Previously, he was the Associate Director of the MxR Lab at the Institute for Creative Technologies and a Research Assistant Professor in the Department of Computer Science at the University of Southern California. His research interests are situated at the intersection of virtual/augmented reality and HCI, encompassing immersive technologies, 3D user interfaces, and spatial interaction techniques. He received his Ph.D. from the Department of Computer Science at the University of North Carolina at Charlotte in 2010. Dr. Suma Rosenberg's research has been recognized with multiple best paper awards and has been funded by NSF, ARL, ONR, and DARPA. Over the past decade, he has also directed the development of multiple publicly released free software projects and contributed to an opensource technology initiative that has had a majo 
Tue Feb 25 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Feb 24 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium  Canceled Canceled 
Mon Feb 24 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Feb 24 
Student Number Theory Seminar3:35pm  Vincent Hall 570The Satake equivalence I: The classical formulation John O'Brien Abstract:When studying the representation theory of reductive groups, one runs into a mysterious phenomenon: a certain duality between certain groups. In 1963, Ichir? Satake gave one of the first attempts of 
Mon Feb 24 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Feb 24 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Feb 21 
MCFAM Seminar5:30pm  VinH 162020 Winter FM Modeling Workshop Presentations 2020 Financial Mathematics (FM) Modeling Workshop Graduate Students, University of Minnesota Abstract:Two teams of Financial Mathematics graduate students will present the results of their projects completed over an intensive 10day winter workshop. The first presentation will be on Data Analysis, Visualization and Statistical/Machine Learning Modeling for Mortgage Prepayment and Delinquency Rates. The Industry Mentor for this project , in attendance for the talk, was: He LuThe second presentation will be on Inflation Rate Curve Modeling. This project was led by Industry Mentor Matt Abroe. 
Fri Feb 21 
Combinatorics Seminar3:35pm  Vincent Hall 570Separable elements and splittings of Weyl groups Yibo Gao, MIT Abstract:We introduce separable elements in finite Weyl groups, generalizing the wellstudied class of separable permutations. They enjoy nice properties in the weak Bruhat order, enumerate faces of the graph associahedron of the corresponding Dynkin diagrams, and can be characterized by pattern avoidance in the sense of Billey and Postnikov. We then prove that the multiplication map W/V×V?WW/V×V?W for a generalized quotient of the symmetric group is always surjective when V is a principal order ideal, providing the first combinatorial proof of an inequality due originally to Sidorenko in 1991, answering an open problem of Morales, Pak, and Panova. We show that this multiplication map is a bijection if and only if V is an order ideal in the right weak order generated by a separable element, answering an open question of Björner and Wachs in 1988. This is joint work with Christian Gaetz. 
Fri Feb 21 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Feb 21 
Probability Seminar2:30pm  Vincent Hall 213Robust Representation for Graph Data Dongmian Zou, UMN Abstract:Modern data are usually highdimensional with noise and corruption. A useful representation of data has to be robust and address the data structure. In this talk, I will first present a class of robust models called the scattering transform that can be used to generated features from graph data. In graph scattering transforms, the representation is generated in an unsupervised manner based on graph wavelets. It is approximately invariant to permutations and stable to signal or graph manipulations. Numerical results show that it works effectively for classification and community detection problems. Next, I will address how the structure of data can be found using autoencoders. Indeed, in the framework of autoencoders, graph scattering transform can be applied to the important task of graph generation. Specifically, I will illustrate its application in generating molecular samples. 
Fri Feb 21 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Feb 21 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Profiles of Math Careers in the Industry Martin Lacasse, ExxonMobil Abstract:While the majority of PhD students graduating in math and physics end up being employed by the industry, there is relatively little information of career opportunities in the industry being presented to students during their graduate studies. This presentation aims at providing some real examples of career paths for mathematicians in the industry, and describing specific problems being addressed by them. The talk is intended to be an informal discussion around how to better prepare oneself to address the challenges raised by pursuing a career in the industry. A FrenchCanadian native, Martin Lacasse completed undergraduate degrees in both chemistry (Montreal) and physics (Concordia) where he graduated first of his promotion. He then studied at McGill University where he earned a M.Sc. and a Ph.D. in Physics, studying problems in statistical mechanics related to critical phenomena and phase transitions using largescale computers. After his Ph.D., Lacasse moved to Princeton University for a joint postdoctoral fellowship with the Corporate Research Laboratory (CSR) of Exxon Research and Engineering. Shortly after in 1995, he joined the lab and worked on the thermodynamics of polymer interfaces and on the rheology of compressed emulsions. Lacasse is currently leading a team of researchers at CSR modeling the effects of induced seismicity during oil and gas production. His current research interests also include experimental design problems in the field of PDEconstrained optimization and the packing of nonspherical particles. Over the years, Lacasse has been recognized as a leader in highperformance computing. 
Fri Feb 21 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Feb 21 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar TBA 
Thu Feb 20 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Feb 20 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Wed Feb 19 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Tue Feb 18 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Feb 18 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Feb 18 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Feb 18 
IMA Data Science Lab Seminar1:25pm  Lind 305From Clustering with Graph Cuts to Isoperimetric Inequalities: Quantitative Convergence Rates of Cheeger Cuts on Data Clouds Nicolas Garcia Trillos, University of Wisconsin, Madison Abstract:Graph cuts have been studied for decades in the mathematics and computer science communities. For example, a celebrated result in optimization relates the cut minimization problem (under some membership constraints) with a maximum flow problem via the well known max flowmin cut duality theorem. Another very important problem formulated in the computer science community that uses graph cuts is motivated by data clustering: while direct minimization of a graph cut is reasonable as it penalizes the size of interfaces, the optimization is not able to rule out partitions of data into groups that are highly asymmetric in terms of size. In order to avoid trivial partitions, and provide a more reasonable clustering approach, the original optimization of graph cuts is modified by adding an extra balancing term to the objective function in either additive or multiplicative form. A canonical example, with historical motivation, is the so called Cheeger cut problem. Minimization of Cheeger cuts for data clustering is on the one hand intuitively motivated, but on the other, is a highly nonconvex optimization problem with a pessimistic NP hard label tamped on it (at least in a worst case scenario setting). Nevertheless, in the past decade or so, several algorithmic improvements made the minimization of Cheeger cuts more feasible, and at the same time there was a renewed interest in studying statistical properties of Cheeger cuts. New analytical ideas have provided new tools to attack problems that were elusive using classical approaches from statistics and statistical learning theory. Despite the advances, several questions remain unanswered. The purpose of this talk is to present some of these theoretical developments, with emphasis on new results where, for the first time, high probability converge rates of Cheeger cuts of proximity graphs over data clouds are deduced. These quantitative convergence rates are obtained by building bridges between the original clustering problem and another field within the mathematical analysis community that has seen enormous advancements in the past few years: quantitative isoperimetric inequalities. This connection serves as a metaphor for how the mathematical analyst may be able to contribute to answer theoretical questions in machine learning, and how one may be able to deduce statistical properties of solutions to learning optimization problems that have a continuum counterpart. 
Tue Feb 18 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Feb 17 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Feb 17 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Direct Sampling Algoritmis in Inverse Scattering Isaac Harris, Purdue University Abstract:In this talk, we will discuss a recent qualitative imaging method referred to as the Direct Sampling Method for inverse scattering. This method allows one to recover a scattering object by evaluating an imaging functional that is the innerproduct of the farfield data and a known function. It can be shown that the imaging functional is strictly positive in the scatterer and decays as the sampling point moves away from the scatterer. The analysis uses the factorization of the farfield operator and the FunkeHecke formula. This method can also be shown to be stable with respect to perturbations in the scattering data. We will discuss the inverse scattering problem for both acoustic and electromagnetic waves. 
Mon Feb 17 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Feb 17 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Feb 17 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Feb 14 
Combinatorics Seminar3:35pm  Vincent Hall 570Combinatorics of the doubledimer model Helen Jenne, Oregon Abstract:In this talk we will discuss a new result about the doubledimer model: under certain conditions, the partition function for doubledimer configurations of a planar bipartite graph satisfies an elegant recurrence, related to the DesnanotJacobi identity from linear algebra. A similar identity for the number of dimer configurations (or perfect matchings) of a graph was established nearly 20 years ago by Kuo 
Fri Feb 14 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Feb 14 
Probability Seminar2:30pm  Vincent Hall 213Order of Fluctuations of the SherringtonKirkpatrick Model at Critical Temperature WeiKuo Chen, UMN Abstract:I will discuss the order of fluctuations in the SherringtonKirkpatrick mean field spin glass model. In particular, I will focus on the predictions concerning the free energy and present an elementary approach for obtaining a logarithmic bound on its variance at the critical temperature. 
Fri Feb 14 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Feb 14 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Feb 14 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Tate Resolutions and Horrocks Splitting Criterion Mahrud Sayrafi , Abstract:I will talk about the two papers EisenbudFløystadSchreyer2003 and EisenbudErmanSchreyer2015 in which they introduce Tate resolutions for projective spaces and products of projective spaces. As an application, I will talk about Horrocks' criterion for vector bundles in those settings. 
Thu Feb 13 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Feb 13 
Special Events and Seminars2:30pm  Vincent Hall 570Vector Bundles on the Projective Space Mahrud Sayrafi, University of Minnesota Abstract:I will start with the basics of line bundles and vector bundles in commutative algebra, specifically over the projective space. This is an introduction for the talk on Friday at the Commutative Algebra Seminar about the Tate resolutions for projective spaces and products of projective spaces. 
Wed Feb 12 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Tue Feb 11 
Colloquium3:30pm  Vincent Hall 16Understanding maps between Riemann surfaces Felix Janda, Institute for Advanced Study in Princeton Abstract:Moduli spaces of Riemann surfaces are a fundamental object in algebraic geometry. Their geometry is rich and holds many outstanding mysteries. One way to probe genus g Riemann surfaces is to understand the maps they admit to the simplest Riemann surface, the Riemann sphere. In my talk, I will describe one facet of this approach, a formula for the double ramification cycle (joint work with R. Pandharipande, A. Pixton and D. Zvonkine). Along the way, we will see connections to combinatorics, number theory and symplectic geometry. 
Tue Feb 11 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Feb 11 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Feb 11 
IMA Data Science Lab Seminar1:25pm  Lind 305Function Space MetropolisHastings Algorithms with NonGaussian Priors Bamdad Hosseini, California Institute of Technology Abstract:MetropolisHastings (MH) algorithms are one of the most widely used methods for inference. In this talk we discuss some ideas for designing new MH algorithms that are reversible with I am a von Karman instructor in the Department of Computing and Mathematical Sciences at California Institute of Technology, sponsored by Prof. Andrew Stuart. Prior to that I received my Ph.D. in Applied and Computational Mathematics in the Department of Mathematics at Simon Fraser University with of Profs. Nilima Nigam and John Stockie. I work on problems at the interface of probability, statistics and applied mathematics with a particular focus on the analysis, development and application of computational methods for estimating parameters and quantifying uncertainty. 
Tue Feb 11 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Feb 10 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Feb 10 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Feb 10 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Feb 10 
Student Number Theory Seminar3:25pm  Vincent Hall 570The Conditional Probability That an Elliptic Curve Has a Rational Subgroup of Order 5 or 7 Meagan Kenney Abstract:Let E be an elliptic curve over the rationals. Divisibility of the set of rational points on E by some integer m can occur locally or globally. If E has global divisibility by m, then E has local divisibility by m; however, work of Katz shows that the converse is only guaranteed up to isogeny. Cullinan and Voight showed that the probability than an elliptic curve has global divisibility by an integer m is nonzero for all integers m allowed by Mazur's classification of rational torsion on elliptic curves. In this talk, I will discuss the probability that E has global divisibility by 5 or 7, given that E has local divisibility by 5 or 7, respectively. 
Mon Feb 10 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Feb 07 
MCFAM Seminar5:30pm  Vincent Hall 16Pricing in Contractual Freight Compared to Finance Kaisa Taipale, C.H. Robinson Abstract:In this talk, I'll discuss the contractual freight business, in which a large shipper makes a contract with a company like CH Robinson to procure carriers (trucks) for their goods over the course of a year for a given rate, as opposed to using the volatile "spot" or transactional market. Because these yearlong contracts aren't legally binding, some shippers treat them more like an American option on the underlying price of freight, but this has gametheoretic economic consequences for the shipper! Dr. Taipale, Data Scientist at C.H. Robinson will also talk about the data science and mathematical skills that are important for her job at C.H. Robinson
Bio : https://www.linkedin.com/in/kaisataipale2630256/detail/contactinfo/ 
Fri Feb 07 
Combinatorics Seminar3:35pm  Vincent Hall 570Unconditional Reflexive Polytopes McCabe Olsen, Ohio State Abstract:A convex body is unconditional if it is symmetric with respect to reflections in all coordinate hyperplanes. In this paper, we investigate unconditional lattice polytopes with respect to geometric, combinatorial, and algebraic properties. In particular, we characterize unconditional reflexive polytopes in terms of perfect graphs. As a prime example, we study the signed Birkhoff polytope. Moreover, we derive constructions for Galedual pairs of polytopes and we explicitly describe Gröbner bases for unconditional reflexive polytopes coming from partially ordered sets. This is joint work with Florian Kohl (Aalto University) and Raman Sanyal (Goethe Universität Frankfurt). 
Fri Feb 07 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Feb 07 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Feb 07 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Feb 07 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Feb 07 
Commutative Algebra Seminar12:20pm  Vincent Hall 213On a question of Dutta, joint with Linquan Ma and Anurag Singh Uli Walther, Purdue Abstract:For a local ring (A,m) of dimension n,we study the natural map from the nth Koszul cohomology on a minimal set of generators of m to the top local cohomology of A supported at m. We construct complete normal domains for which this map is zero, thus answering a question of Dutta in the negative. If time permits, we present precise information on the kernel of this map for a large class of StanleyReisner rings. 
Thu Feb 06 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Feb 06 
Special Events and Seminars2:30pm  Vincent Hall 570Student Commutative Algebra Seminar 
Wed Feb 05 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Tue Feb 04 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Feb 04 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Feb 04 
Dynamical Systems2:30pm  Vincent Hall 213Spectral Stability, the Maslov Index, and Spatial Dynamics Margaret Beck, Boston University Abstract:Understanding the spectral stability of solutions to partial differential equations is an important step in predicting longtime dynamics. Recently, it has been shown that a topological invariant known as the Maslov Index can play an important role in determining spectral stability for systems that have a symplectic structure. In addition, related ideas have lead to a suggested generalization of the notion of spatial dynamics to general, multidimensional spatial domains. In this talk, the notions of spectral stability, the Maslov Index, and spatial dynamics will be introduced and an overview of recent results will be given. 
Tue Feb 04 
IMA Data Science Lab Seminar1:25pm  Lind 305Different Aspects of Registration Problem Yuehaw Khoo, University of Chicago Abstract:In this talk, we discuss several variants of the rigid registration problem, i.e aligning objects via rigid transformation. In the simplest scenario of pointset registration where the correspondence between points are known, we investigate the robustness of registration to outliers. We also study a convex programming formulation of pointset registration with exact recovery, in the situation where both the correspondence and alignment are unknowns. Lastly, an important registration problem arises in Cryoelectron microscopy for protein structuring will be discussed. This talk is based on joint works with Ankur Kapoor, Joe Kileel, Boris Landa, Cindy Orozco, Amit Singer, Nir Sharon, and Lexing Ying. Yuehaw Khoo is an assistant professor in the statistics department of University of Chicago. Prior to this, he was a postdoc in Stanford and graduate student in Princeton. He is interested in scientific computing problems in protein structure determination and quantum manybody physics. In these problems, he focuses on nonconvex, discrete or large scale optimization and representing highdimensional functions using neuralnetwork and tensor network. 
Tue Feb 04 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Feb 03 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207On the final frontiers in computational mathematics Anders Hansen, Cambridge Abstract:Core problems in computational mathematics include computing spectra of operators, solutions to linear PDEs, convex optimisation problems etc., and these areas have been intensely investigated over the last half century. However, there are still fundamental open problems. For example, despite more than 90 years of quantum mechanics, it is still unknown whether it is possible to compute spectra of Schrodinger operators with bounded potentials. Moreover, how to compute minimisers of linear programs (LP) with rational inputs has been known since the 1950s, however, what happens if the input is irrational? Can one accurately compute minimisers of LPs if, as in compressed sensing, the matrix has rows from the discrete cosine transform? Furthermore, do there exist algorithms that can handle all linear Schrodinger PDEs? And, if not, which can be handled and which can never be solved? We will discuss solutions to many of these open problems and provide some potentially surprising results. For example, despite being open for decades, the problem of computing spectra of Schrodinger operators with bounded potentials is not harder than computing spectra of diagonal infinite matrices, the easiest of computational spectral problems. Moreover, for LPs with irrational inputs we have the following phenomenon. For any integer K > 2 there exists a class of well conditioned inputs so that no algorithm can compute K correct digits of a minimiser, however, there exists an algorithm that can compute K1 correct digits. But any algorithm producing K1 correct digits will need arbitrarily long time. Finally, computing K2 correct digits can be done in polynomial time in the number of variables. 
Mon Feb 03 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311Applied and Computational Mathematics Seminar 
Mon Feb 03 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Feb 03 
Student Number Theory Seminar3:25pm  Vincent Hall 570Selfadjoint operators and zeta function Paul Garrett Abstract:One hundred years ago, when the theory of selfadjoint operators was 
Mon Feb 03 
Topology Seminar2:30pm  Vincent Hall 311Topology Seminar 
Fri Jan 31 
Combinatorics Seminar3:35pm  Vincent Hall 570Weak order and descents for monotone triangles Vic Reiner Abstract:(joint work with Zach Hamaker; arXiv:1809.1057) Monotone triangles are combinatorial objects in bijection with alternating sign matrices, a fascinating generalization of permutation matrices. We will review this connection, and the fact that strong Bruhat order on permutations has a natural extension to monotone triangles. We will then explain an analogous extension of the weak Bruhat order on permutations to monotone triangles. This comes from extending the notions of descents in permutations and the "bubblesorting" action of the 0Hecke algebra on permutations to monotone triangles. We will also explain one of our motivations: to give a natural family of shellings for Terwilliger's recently defined order on subsets. 
Fri Jan 31 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Jan 31 
Probability Seminar2:30pm  Vincent Hall 213Nearcritical avalanches in 2D frozen percolation and forest fires WaiKit Lam, UMN Abstract:We consider (volume)frozen percolation on the triangular lattice. The model can be described informally as follows. Fix a large integer $N$. Initially, all vertices are vacant. We let clusters grow (vertices become occupied) as long as their volume is strictly smaller than $N$, and they stop growing (they "freeze") when their volume becomes at least $N$. A vertex $v$ is frozen if it belongs to an occupied cluster with volume at least $N$. In this model, there exists a sequence of "exceptional scales" $(m_k(N))$: roughly speaking, if we consider frozen percolation in a box of side length $m_k(N)$, then as $N\to\infty$, the probability that $0$ is frozen in the final configuration is bounded away from $0$; while if we consider the process in a box of side length that is far from $m_k(N)$ and $m_{k+1}(N)$ (but between them), then as $N\to\infty$, the corresponding probability will go to $0$. The limiting exception scale, $m_\infty(N)$, is not studied and almost nothing is known. In an ongoing project with Pierre Nolin, we show that if we consider the process in a box of side length $m_\infty(N)$, then there are "avalanches" of freezings: the number of frozen circuits surrounding the origin divided by $\log\log{N}$ converges to an explicit constant in probability. If time allows, I will also talk about the analogous result in the forest fire process. 
Fri Jan 31 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Jan 31 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305How NextEra Analytics Applies Math to Problems in Coupled Renewable and Energy Storage Systems Madeline Handschy, NextEra Analytics Inc Abstract:Renewable energy sources  solar and wind  are inherently variable, and unlike a traditional power plant, energy generation can't be 'turned up' or 'turned down' at will. In the past several years, the rapidly falling price of Lithium Ion batteries and related technology has made it more feasible than ever to build solar or wind farms coupled with energy storage capabilities to mitigate some of the variability of the renewable resource and provide more control over the energy output of the farm. In this talk, I will give an overview of working at NextEra Analytics and give examples of how we are applying math to operate energy storage projects as well as evaluate potential new renewable + energy storage hybrid projects. Madeline graduated in May from the University of Minnesota with a PhD in Mathematics coadvised by Drs. Gilad Lerman and WeiKuo Chen. She started in the Applied Math Group at NextEra Analytics in June and works primarily on math related to energy storage. 
Fri Jan 31 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Jan 31 
Commutative Algebra Seminar12:20pm  Vincent Hall 213Commutative Algebra Seminar 
Thu Jan 30 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Wed Jan 29 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Tue Jan 28 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Jan 28 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Jan 28 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Jan 28 
IMA Data Science Lab Seminar1:25pm  Lind 409Machine Learning Meets Societal Values Steven Wu, University of Minnesota, Twin Cities Abstract:The vast collection of detailed personal data has enabled machine learning to have a tremendous impact on society. Algorithms now provide predictions and insights that are used to make or inform consequential decisions on people. Concerns have been raised that our heavy reliance on personal data and machine learning might compromise peoples privacy, produce new forms of discrimination, and violate other kinds of social norms. My research seeks to address this emerging tension between machine learning and society by focusing on two interconnected questions: 1) how to make machine learning better aligned with societal values, especially privacy and fairness, and 2) how to make machine learning methods more reliable and robust in social and economic dynamics. In this talk, I will provide an overview of my research and highlight some of my recent work on fairness in machine learning and differentially private synthetic data generation. Steven Wu is an Assistant Professor of Computer Science and Engineering at the University of Minnesota. His research interests are in algorithms and machine learning, with a focus on privacypreserving data analysis, algorithmic fairness, and algorithmic economics. From 2017 to 2018, he was a postdoc researcher at Microsoft ResearchNew York City in the Machine Learning and Algorithmic Economics groups. In 2017, he received his Ph.D. in computer science under the supervision of Michael Kearns and Aaron Roth at the University of Pennsylvania, where his doctoral dissertation received Penns Morris and Dorothy Rubinoff Award for best thesis. His research is supported by an Amazon Research Award, a Facebook Research Award, a Mozilla research grant, a Google Faculty Research Award, a J.P. Morgan Research Faculty Award, and the National Science Foundation. 
Tue Jan 28 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Jan 27 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Jan 27 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 311An inverse problem on Light Sheet Fluorescence Microscopy Benjamin Palacios, University of Chicago Abstract:In Light Sheet Fluorescence Microscopy a density of fluorescent material (fluorophores) needs to be reconstructed through a process that consists in the application of a thin sheet of light that stimulates fluorophores, inducing the emission of fluorescent light that is recorderded and which constitute our measurements. In this talk I will present a mathematical model for this twostep process as well as the inverse problem arising from it. Uniqueness and stability of the inverse problem will be discussed. 
Mon Jan 27 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jan 27 
Student Number Theory Seminar3:25pm  Vincent Hall 570Student Number Theory Seminar 
Mon Jan 27 
Topology Seminar2:30pm  Vincent Hall 311Smooth 4manifolds and the geometry of 3manifolds Matthew Stoffregen, MIT Abstract:One of the interests of lowdimensional topologists is 
Fri Jan 24 
MCFAM Seminar5:30pm  Vincent Hall 16U of MN Women in Math and Stats Graduate Team  2019 MinneMUDAC Award Winning Analytics Presentation on Commodity Pricing Cora Brown, Somyi Baek, Sarah Milstein, and Yu Yang, University of Minnesota Abstract:University of Minnesota mathematics and statistics graduate students formed a team called "Women in Math and Stats" and competed in the MinneMUDAC 2019 Challenge. They took 2nd place in a field of 24 teams in the graduate division of the challenge. They also received the Analytic Acumen Award for the 2nd year in a row. This years challenge required students to analyze a variety of data to predict trends in soybean prices. Teams were evaluated based on a number of factors, including data preparation, team synergy, and communication of results. Teams in the Undergraduate and Graduate divisions were also scored on the accuracy of their predictions. The challenge and data were curated by Farm Femmes. We firmly believe that investing in the next generation grows the future, said Karen Hildebrand, CoFounder of Farm Femmes. Some days the seeds we plant are literal as farmers, but MinneMUDAC gave us the opportunity to grow the knowledge of agriculture and agtech.Members of the team who will presenting include: Cora Brown, Somyi Baek, Sarah Milstein, and Yu Yang. Their faculty advisor was Dr. Gilad Lerman. 
Fri Jan 24 
Lie Theory Seminar3:30pm  Vincent Hall 209Lie Theory Seminar 
Fri Jan 24 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 364Reading Seminar on Automorphic Forms 
Fri Jan 24 
Special Events and Seminars1:00pm  Vincent Hall 301pAdic Cohomology, Exponential Sums, and Hypergeometric Functions 
Fri Jan 24 
Commutative Algebra Seminar12:20pm  VinH 203ACommutative Algebra Seminar 
Thu Jan 23 
Colloquium3:35pm  Vincent Hall 16Modularity and the Hodge/Tate conjectures for some selfproducts Laure Flapan, MIT Abstract:If X is a smooth projective variety over a number field, the Hodge and Tate conjectures describe how information about the subvarieties of X is encoded in the cohomology of X. We explore the role that certain automorphic representations, called algebraic Hecke characters, can play in understanding which cohomology classes of X arise from subvarieties. We use this to deduce the Hodge and Tate conjectures for certain selfproducts of varieties, including some selfproducts of K3 surfaces. This is joint work with J. Lang. 
Wed Jan 22 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Tue Jan 21 
Colloquium3:30pm  Vincent Hall 16Optimal Transport as a Tool in Analytic Number Theory and PDEs Stefan Steinerberger, Yale University Abstract:Optimal Transport is concerned with the question of how to best move one measure to another (this could be sand on a beach or products from a warehouse to consumers). I will explain the basic definition of Wasserstein distance and then describe how it can be used as a tool to say interesting things in other fields. (1) How to get new regularity statements for classical objects in number theory almost for free (irrational rotations on the torus, quadratic residues in finite fields). (2) How to best distribute coffee shops over downtown Minneapolis. (3) Finally, how to obtain higher dimensional analogues of classical SturmLiouville theory: simply put, SturmLiouville theory says that eigenfunctions of the operator Ly = y''(x) +p(x)y(x) (think of sin(kx) and cos(kx)) cannot have an arbitrary number of roots; we present a generalization to higher dimensions that is based on a simple (geometric) inequality. 
Tue Jan 21 
Special Events and Seminars3:30pm  Vincent Hall 364Arithmetic Geometry Seminar 
Tue Jan 21 
Dynamical Systems2:30pm  Vincent Hall 213Dynamical Systems Seminar 
Tue Jan 21 
IMA Data Science Lab Seminar1:25pm  Lind 305Linear Unbalanced Optimal Transport Matthew Thorpe, University of Cambridge Abstract:Optimal transport is a powerful tool for measuring the distances between This is joint work with Bernhard Schmitzer (TU Munich). Matthew is a research fellow in the Cantab Capital Institute for the 
Tue Jan 21 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Jan 20 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Tue Jan 14 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Jan 13 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Tue Jan 07 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Jan 06 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Tue Dec 31 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Dec 30 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Tue Dec 24 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Dec 23 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Dec 20 
Combinatorics Seminar3:30pm  Vincent Hall 570Combinatorics Seminar 
Fri Dec 20 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Thu Dec 19 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Dec 19 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar TBA 
Thu Dec 19 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Dec 18 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Dec 18 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Tue Dec 17 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Dec 17 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Dec 17 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Dec 16 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Dec 16 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Dec 16 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Dec 13 
Combinatorics Seminar3:30pm  Vincent Hall 570Combinatorics Seminar No Seminar  Final Exams 
Fri Dec 13 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar 
Fri Dec 13 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Dec 13 
Special Events and Seminars1:25pm  Vincent Hall 213"pAdic Cohomology, Exponential Sums, and Hypergeometric Functions TBA 
Thu Dec 12 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Dec 12 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Dec 12 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar TBA 
Thu Dec 12 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar 
Thu Dec 12 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Dec 11 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Dec 11 
PDE Seminar3:35pm  Vincent Hall 570Quantitative stochastic homogenization via Malliavin calculus Antoine Gloria, Sorbonne Université Abstract:Abstract: This talk is about stochastic homogenization of linear elliptic equations in divergence form. Let $a(x)=h(G(x))$ be a diffusion coefficient field, where $h$ is a Lipschitz function and $G$ is a Gaussian field (with possibly thick tail). Solutions $u_\varepsilon$ of elliptic equations $\nabla \cdot a(\cdot/\varepsilon) \nabla u_\varepsilon = \nabla \cdot f$ in $\mathbb R^d$ with such random heterogeneous coefficients $a$ both oscillate spatially and fluctuate randomly at scale $\varepsilon >0$. I will show how suitable quantitative twoscale expansions allow one to reduce the analysis of oscillations and fluctuations of solutions to bounds on the corrector and fluctuations of the homogenization commutator, respectively. The main probabilistic ingredient is Malliavin calculus, and the main analytical ingredient is largescale elliptic regularity. This is based on joint works with Mitia Duerinckx, Julian Fischer, Stefan Neukamm, and Felix Otto. 
Wed Dec 11 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Dec 10 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Dec 10 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Dec 10 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Dec 10 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology Seminar TBA 
Tue Dec 10 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Dec 09 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Gradient Flows: From PDE to Data Analysis Franca Hoffman, Caltech Abstract:Certain diffusive PDEs can be viewed as infinitedimensional gradient flows. This fact has led to the development of new tools in various areas of mathematics ranging from PDE theory to data science. In this talk, we focus on two different directions: modeldriven approaches and datadriven approaches. 
Mon Dec 09 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Dec 09 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Dec 09 
Topology Seminar2:30pm  Ford Hall 110Topology Seminar TBA 
Mon Dec 09 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Dec 06 
MCFAM Seminar5:30pm  Vincent Hall 16GUN VIOLENCE: ACTUARIAL ANALYSIS AND MATHEMATICAL MODELING Kristen Moore, University of Michigan Abstract:Firearm deaths and injuries are a significant problem in the United States. Indeed, the American Medical Association recently called firearm violence a public health crisis and called for a comprehensive public health response and solution. Gun violence in America exacts a significant toll on our society in both human and economic terms. Some argue that Americans have a moral obligation to address the issue of gun violence. But even from a more concrete perspective, the economic cost of firearms directly impacts the financial outcomes of insurers and taxpayers. There is a clear need for unbiased and objective research on the societal and economic impact of firearms. Actuaries are well positioned to study the mortality and morbidity related to firearms, both to quantify the risk and to inform governmental and public health interventions to mitigate the risk associated with firearms. Yet there is little on the topic in the actuarial and insurance literature. In this talk, I will provide a brief overview on the scope of firearm deaths and injuries and examine the extent to which actuaries and insurance professionals have studied or addressed the issue. I will compare firearm risk to risks that are considered in the underwriting process for life and homeowners insurance. I will describe some existing insurance products related to firearm risk as well as proposed legislation regarding gun liability insurance. In a different vein, if time permits, I will discuss preliminary work on a dynamical systems model of gun violence within a population. We are studying how, in an idealized model, changes to various policy parameters affect the longterm behavior of a system. Finally, I will describe some of the many open questions related to gun violence that are amenable to study by actuaries and mathematicians. Bio: https://sites.lsa.umich.edu/ksmoore/ 
Fri Dec 06 
Lie Theory Seminar3:35pm  Vincent Hall 1Special modular forms on exceptional groups Aaron Pollack, Duke University Abstract:Classically, a Siegel modular form is said to be singular or distinguished if many of its Fourier coefficients are 0, in a precise sense. I will explain the construction of singular and distinguished modular forms on the exceptional groups E_6, E_7, E_8. Moreover, time permitting, I will also explain an analogue of the SaitoKurokawa lift, which produces cusp forms on Spin(8) and the exceptional group G_2 out of holomorphic Siegel modular forms on Sp(4). 
Fri Dec 06 
Combinatorics Seminar3:30pm  Vincent Hall 570A noniterative formula for straightening fillings of Young diagrams Reuven Hodges, UIUC Abstract:Young diagrams are fundamental combinatorial objects in representation theory and algebraic geometry. Many constructions that rely on these objects depend on variations of a straightening process that expresses a filling of a Young diagram as a sum of semistandard tableaux subject to certain relations. It has been a longstanding open problem to give a noniterative formula for this straightening process. In this talk I will give such a formula. I will then use this noniterative formula give a proof that the coefficient of the leading term in the straightening is either 1 or 1, generalizing a theorem of Gonciulea and Lakshmibai. 
Fri Dec 06 
Probability Seminar2:30pm  Vincent Hall 311Gibbsian line ensembles and loggamma polymers Xuan Wu, Columbia University Abstract:In this talk we will first give an overview of the known 
Fri Dec 06 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar 
Fri Dec 06 
Math Biology Seminar2:30pm  VinH 209Math Biology Seminar 
Fri Dec 06 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Dec 06 
Special Events and Seminars1:25pm  Vincent Hall 213"pAdic Cohomology, Exponential Sums, and Hypergeometric Functions TBA 
Fri Dec 06 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Lecture Whitney Moore, University of Minnesota, Twin Cities 
Fri Dec 06 
IMA Data Science Lab Seminar1:25pm  Lind 305Probabilistic Preference Learning with the Mallows Rank Model for Incomplete Data Arnoldo Frigessi, Oslo University Hospital Abstract:Personalized recommendations are useful to assist users in their choices in webbased market places, entertainment engines, information providers. Learning individual preferences is an important step. Users express their preferences by rating, ranking, (possibly inconsistently) comparing, liking and clicking items. Such data contain information about the individual users ranking of the items. Clickthrough data can be seen as (consistent) pair comparisons. The Mallows rank model allows to analyse rank data, but its computational complexity has limited its use to a particular form, based on Kendalls distance. We developed new computationally tractable methods for Bayesian inference in Mallows models that work with any rightinvariant distance. Our method performs inference on the latent consensus ranking of all items and on the individual latent rankings by Bayesian augmentation. Current popular recommendation algorithms are based on matrix factorisations, have high accuracy and achieve good clickthrough rates. However diversity of the recommended items is often poor and most algorithms do not produce interpretable uncertainty quantifications of the recommendations. With a simulation study and real life data examples, we demonstrate that compared to matrix factorisation approaches, our Bayesian Mallows method makes personalized recommendations mpared to matrix factorisation approaches, our Bayesian Mallows method makes personalized recommendations. Arnoldo Frigessi is professor of statistics at the University of Oslo, leads the Oslo Center for Biostatistics and Epidemiology and is director of BigInsight. BigInsight is a centre of excellence for researchbased innovation, a consortium of industry, business, public actors and academia, developing model based machine learning methodologies for big data. Originally from Italy, where he had positions in Rome and Venice, he moved to Norway in 2019 as a researcher at the Norwegian Computing Centre, before he became professor at the University of Oslo. Frigessi has developed statistical methodology motivated by specific problems in science, technology and industry. He has designed stochastic models to study principles, dynamics and patterns of complex dependence. Inference is usually based on computationally intensive stochastic algorithms. Currently, he has research collaborations in genomics, personalised therapy in cancer, infectious disease models, eHealth research, personalised and viral marketing, s 
Thu Dec 05 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Dec 05 
Colloquium3:35pm  Vincent Hall 16Modular forms on exceptional groups Aaron Pollack, Duke Abstract:When G is a reductive (noncompact) Lie group, one can consider automorphic forms for G. These are functions on the locally symmetric space X_G associated to G that satisfy some sort of nice differential equation. When X_G has the structure of a complex manifold, the _modular forms_ for the group G are those automorphic forms that correspond to holomorphic functions on X_G. They possess close ties to arithmetic and algebraic geometry. For certain exceptional Lie groups G, the locally symmetric space X_G is not a complex manifold, yet nevertheless possesses a very special class of automorphic functions that behave similarly to the holomorphic modular forms above. Building upon work of Gan, Gross, Savin, and Wallach, I will define these modular forms and explain what is known about them. 
Thu Dec 05 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar McCleary Philbin, University of Minnesota 
Thu Dec 05 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Einstein's gravity and stability of black holes PeiKen Hung, MIT Abstract:Though Einstein's fundamental theory of general relativity has already celebrated its one hundredth birthday, there are still many outstanding unsolved problems. The Kerr stability conjecture is one of the most important open problems, which posits that the Kerr metrics are stable solutions of the vacuum Einstein equation. Over the past decade, there have been huge advances towards this conjecture based on the study of wave equations in black hole spacetimes and structures in the Einstein equation. In this talk, I will discuss the recent progress in the stability problems with special focus on the wave gauge. 
Wed Dec 04 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Dec 04 
PDE Seminar3:35pm  Vincent Hall 570Multiscale analysis of Jordan curves Benjamin Jaye, Clemson University Abstract:In this talk we will describe how one can detect regularity in Jordan curves through analysis of associated geometric square functions. We will particularly focus on the resolution to a conjecture of L. Carleson. Joint work with Xavier Tolsa and Michele Villa (https://arxiv.org/abs/1909.08581). 
Wed Dec 04 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Dec 03 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Dec 03 
Colloquium3:30pm  Vincent Hall 16Mirror symmetry and canonical bases for quantum cluster algebras Travis Mandel, Univ. of Edinburgh Abstract:Mirror symmetry is a phenomenon which relates the symplectic geometry of one space X to the algebraic geometry of another space Y. One consequence is that a canonical basis of regular functions on Y can be defined in terms of certain counts of holomorphic curves in X. I'll discuss the application of this to (quantum) cluster algebras  certain combinatorially defined algebras whose definition was motivated by the appearance of canonical bases in representation theory and Teichmüller theory. 
Tue Dec 03 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Dec 03 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Dec 03 
IMA Data Science Lab Seminar1:25pm  Lind 305Exploiting Group and Geometric Structures for Massive Data Analysis Zhizhen (Jane) Zhao, University of Illinois at UrbanaChampaign Abstract:In this talk, I will introduce a new unsupervised learning framework for data points that lie on or close to a smooth manifold naturally equipped with a group action. In many applications, such as cryoelectron microscopy image analysis and shape analysis, the dataset of interest consists of images or shapes of potentially high spatial resolution, and admits a natural group action that plays the role of a nuisance or latent variable that needs to be quotient out before useful information is revealed. We define the pairwise groupinvariant distance and the corresponding optimal alignment. We construct a graph from the dataset, where each vertex represents a data point and the edges connect points with small groupinvariant distance. In addition, each edge is associated with the estimated optimal alignment group. Inspired by the vector diffusion maps proposed by Singer and Wu, we explore the cycle consistency of the group transformations under multiple irreducible representations to define new similarity measures for the data. Utilizing the representation theoretic mechanism, multiple associated vector bundles can be constructed over the orbit space, providing multiple views for learning the geometry of the underlying base manifold from noisy observations. I will introduce three approaches to systematically combine the information from different representations, and show that by exploring the redundancy created artificially across irreducible representations of the transformation group, we can get drastically improved nearest neighbor identification, when a large portion of the true edges are corrupted. I will also show the application in cryoelectron microscopy image analysis. 
Tue Dec 03 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar No Seminar 
Mon Dec 02 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Towards personalized computer simulation of breast cancer treatment Arnoldo Frigessi , University of Oslo Abstract:Current personalized cancer treatment is based on biomarkers which allow assigning each patient to a subtype of the disease, for which treatment has been established. Such stratifiedpatient treatments represent a first important step away from onesizefitsall treatment.However, the accuracy of disease classification comes short in the granularity of thepersonalization: it assigns patients to one of a few classes, within which heterogeneity inresponse to therapy usually is still very large. In addition, the combinatorial explosivequantity of combinations of cancer drugs, doses and regimens, makes clinical testingimpossible. We propose a new strategy for personalised cancer therapy, based on producing acopy of the patients tumour in a computer, and to expose this synthetic copy to multiplepotential therapies. We show how mechanistic mathematical modelling, patient specificinference and simulation can be used to predict the effect of combination therapies in a breastcancer. The model accounts for complex interactions at the cellular and molecular level, andis able of bridging multiple spatial and temporal scales. The model is a combination ofordinary and partial differential equations, cellular automata and stochastic elements. Themodel is personalised by estimating multiple parameters from individual patient data,routinely acquired, including histopathology, imaging and molecular profiling. The resultsshow that mathematical models can be personalized to predict the effect of therapies in eachspecific patient. The approach is tested with data from five breast tumours collected in arecent neoadjuvant clinical phase II trial. The model predicted correctly the outcome after 12weeks treatment and showed by simulation how alternative treatment protocols would haveproduced different, and some times better, outcomes. This study is possibly the first onetowards personalized computer simulation of breast cancer treatment incorporating relevantbiologicallyspecific mechanisms and multitype individual patient data in a mechanistic andmultiscale manner: a first step towards virtual treatment comparison.Xiaoran Lai, Oliver Geier, Thomas Fleischer, Øystein Garred, Elin Borgen, Simon Funke,Surendra Kumar, Marie Rognes, Therese Seierstad, AnneLise BørressenDale, VesselaKristensen, Olav Engebråten, Alvaro KöhnLuque, and Arnoldo Frigessi, Tow 
Mon Dec 02 
Student Number Theory Seminar3:35pm  Vincent Hall 1Student Number Theory Seminar Henry Twiss 
Mon Dec 02 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Dec 02 
Colloquium3:35pm  Vincent Hall 570Analysis and geometry of free boundaries: recent developments Mariana Smit Vega Garcia, Western Washington University Abstract:In the applied sciences one is often confronted with free boundaries, which arise when the solution to a problem consists of a pair: a function u (often satisfying a partial differential equation (PDE)), and a set where this function has a specific behavior. Two central issues in the study of free boundary problems and related problems in calculus of variations and geometric measure theory are:(1) What is the optimal regularity of the solution u? In this talk, I will overview recent developments in obstacle type problems and almost minimizers of Bernoullitype functionals, illustrating techniques that can be used to tackle questions (1) and (2) in various settings. The study of the classical obstacle problem  one of the most renowned free boundary problems  began in the 60s with the pioneering works of G. Stampacchia, H. Lewy and J. L. Lions. During the past five decades, it has led to beautiful and deep developments in the calculus of variations and geometric partial differential equations. Nowadays obstacle type problems continue to offer many challenges and their study is as active as ever. 
Mon Dec 02 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Dec 02 
Topology Seminar2:30pm  Ford Hall 110Topology and Arithmetic Statistics Weiyan Chen, University of Minnesota Abstract:Topology studies the shape of spaces. Arithmetic statistics studies the behavior of random algebraic objects such as integers and polynomials. I will talk about a circle of ideas connecting these two seemingly unrelated areas. To illuminate the connection, I will focus on three concrete examples: (1) the Burau representation of the braid groups, (2) analytic number theory for effective 0cycles on a variety, and (3) cohomology of the space of multivariate irreducible polynomials. These projects are parts of a broader research program, with numerous contributions by topologists, algebraic geometers, and number theorists in the past decade, and lead to many future directions yet to be explored. 
Mon Dec 02 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Nov 29 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Nov 29 
Combinatorics Seminar3:30pm  Vincent Hall 570Combinatorics Seminar No Seminar 
Fri Nov 29 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar 
Fri Nov 29 
Math Biology Seminar2:30pm  VinH 209Math Biology Seminar 
Fri Nov 29 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Nov 29 
Special Events and Seminars1:25pm  Vincent Hall 213"pAdic Cohomology, Exponential Sums, and Hypergeometric Functions TBA 
Thu Nov 28 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Nov 28 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Nov 28 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar TBA 
Thu Nov 28 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Nov 27 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Nov 27 
PDE Seminar3:35pm  Vincent Hall 570Quantitative Absolute Continuity of Harmonic Measure, and the Lp Dirichlet Problem Steve Hofmann, University of Missouri Abstract:For a domain ? ? Rd, quantitative, scaleinvariant absolute continuity (more precisely, the weakA? property) of harmonic measure with respect to surface measure on ??, is equivalent to the solvability of the Dirichlet problem for Laplaces equation, with data in some Lp space on ??, with p < ?. Drawing an analogy to the famous Wiener criterion, which characterizes the domains in which the classical Dirichlet problem, with continuous boundary data, can be solved, it is of interest to find criteria for Lp solvability, thus allowing for singular boundary data. We shall review known results in this direction, in which (within the past 18 months) a rather complete picture has now emerged. 
Wed Nov 27 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Nov 26 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Nov 26 
Colloquium3:35pm  Vincent Hall 16Schrodinger solutions on sparse and spreadout sets Xiumin Du, University of Maryland Abstract:If we want the solution to the Schrodinger equation to converge to its initial data pointwise, what's the minimal regularity condition for the initial data should be? I will present recent progress on this classic question of Carleson. This pointwise convergence problem is closely related to other problems in PDE and geometric measure theory, including spherical average Fourier decay rates of fractal measures, Falconer's distance set conjecture, etc. All these problems essentially ask how to control Schrodinger solutions on sparse and spreadout sets, which can be partially answered by several recent results derived from induction on scales and BourgainDemeter's decoupling theorem. 
Tue Nov 26 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Nov 26 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology 
Tue Nov 26 
IMA Data Science Lab Seminar1:25pm  Lind 305Information Flow and Security Aspects in 121 Networks Martina Cardone, University of Minnesota, Twin Cities Abstract:In this talk, we will discuss 121 networks, which offer a simple yet informative model for mmWave networks. In such networks, it is assumed that two nodes can communicate only if they point beams at each other, otherwise the signal is received well below the thermal noise floor. The focus of the talk will be on single unicast 121 networks, where the communication from a source to a destination is assisted by a number of relays. In the first part of the presentation, we will characterize the maximum flow of information over such 121 networks. In particular, we will show that the Shannon capacity can be approximated by routing information along a polynomial (in the network size) number of paths between the source and the destination, and that the scheduling of the node beam orientations can be efficiently performed. In the second part of the presentation, we will analyze the security aspect of such 121 networks in the presence of an external eavesdropper who wiretaps a set of edges of her choice. In particular, we will derive secure capacity results, which highlight fundamental differences between the traditional secure network coding and security over 121 networks. Martina Cardone is currently a tenuretrack Assistant Professor within the Electrical and Computer Engineering department at the University of Minnesota. She received her B.Sc. and her M.Sc. in Telecommunications Engineering from Politecnico di Torino, Italy in 2009 and 2011, respectively. As part of a double degree program, she also received a M.Sc. degrees in Telecommunications Engineering from Télécom ParisTech, France in 2011. In 2015, she received her Ph.D. in Electronics and Communications from Télécom ParisTech (with work done at Eurecom in Sophia Antipolis, France), where she worked with Professor Raymond Knopp and Professor Daniela Tuninetti. From July 2015 to August 2017 she was a postdoctoral research fellow in the Electrical and Computer Engineering department at the University of California, Los Angeles, where she worked with Professor Christina Fragouli. From November 2017 to January 2018, she was a postdoctoral associate in the Electrical and Computer Engineering department at the University of Minnesota. She regularly serves on the Technical Program Committee of IEEE workshops and conferences. Her main research interests are in network information theory, wireless communications, network privacy and secrecy, network coding and distributed computing. She was the reci 
Tue Nov 26 
Colloquium1:25pm  Vincent Hall 570Kstability and moduli spaces of Fano varieties Yuchen Liu, Yale University Abstract:Fano varieties are positively curved algebraic varieties which form one of the three building blocks in the classification. Unlike the case of negatively curved varieties, moduli spaces of Fano varieties (even smooth ones) can fail to be Hausdorff. Kstability was originally invented as an algebrogeometric notion characterizing the existence of K\"ahlerEinstein metrics on Fano varieties. Recently, people have found strong evidence toward constructing compact Hausdorff moduli spaces of Fano varieties using Kstability. In this talk, I will discuss recent progress in this approach, including an algebraic proof of the existence of Fano Kmoduli spaces, and describing these moduli spaces explicitly. This talk is partly based on joint works with H. Blum and C. Xu. 
Tue Nov 26 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Nov 25 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Nov 25 
Student Number Theory Seminar3:35pm  Vincent Hall 1Crystalline cohomology and Katz's conjecture Shengkai Mao Abstract:Crystalline cohomology is a type of Weil cohomology theory that fills in the gap at $p$ in the family of $l$adic cohomologies. It's introduced by Alexander Grothendieck and developed by Pierre Berthelot. We will briefly discuss what is crystalline cohomology and why we need it. With the help of Frobenius action, we can define a semilinear morphism on crystalline cohomology which provides a Newton polygon. We will state the Katz's conjecture (which is proved by Mazur and Ogus) (slogan: Newton polygon lies above Hodge polygon) and show some applications (if time permits). 
Mon Nov 25 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Nov 25 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Nov 25 
Topology Seminar2:30pm  Ford Hall 110Topology Seminar TBA 
Mon Nov 25 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Mon Nov 25 
Differential Geometry and Symplectic Topology Seminar10:10am  Vincent Hall 203ADifferential Signatures and Algebraic Curves Michael Ruddy,, Max Planck Institute Abstract:For the action of a group on the plane, the group equivalence problem for curves can be stated as: given two curves, decide if they are related by an element of the group. The signature method, using differential invariants, to answer the local group equivalence problem for smooth curves and its application to image science has been extensively studied. For planar algebraic curves under subgroups of the general linear group, we show that this provides a method to associate a unique algebraic curve to each equivalence class, the algebraic curve's signature curve. However, computing the implicit equation of the signature curve is a challenging problem. In this talk we consider signatures of algebraic curves, show how to compute the degree without computing its defining polynomial explicitly, and present some results on the structure of signature curves for generic algebraic curves of fixed degree. Additionally we show that this leads to a method to solve the group equivalence problem for algebraic curves using numerical algebraic geometry. 
Fri Nov 22 
MCFAM Seminar5:30pm  Vincent Hall 16The impact of negative interest rate policy and its effectiveness of stimulating economic growth Perry Li, University of Minnesota Abstract:According to the Bloomberg Barclays Global Aggregate Index, there were $17 trillion (or 30%) bonds traded with negative yields within that popular fixed income benchmark, at the end of August 2019. Government bonds in Germany, Japan, and Switzerland all carry negative yields  meaning investors will lose money to hold them to maturity. How did we get here? Are those policies introduced by global central banks, after the 2008 financial crisis, effective (to spur inflation)? In this talk, I seek to use some case studies like reserve banking system, asset bubbles, and currency war to explore this topic.Bio: https://www.linkedin.com/in/liyuepeng/ 
Fri Nov 22 
Combinatorics Seminar3:30pm  Vincent Hall 570A Pieri rule for key polynomials Danjoseph Quijada, USC Abstract:The Pieri rule for the product of a Schur function and a single row Schur function is notable for having an elegant bijective proof that can be intuited by the rules concise diagrammatic interpretation, to wit, by appending cells to a Young diagram. Now, key polynomials generalize Schur polynomials to a basis of the full polynomial ring, in which they also refine the Schubert basis via a nice formula. In this talk, I will describe a Pieri rule for the product of a key polynomial and a single row key polynomial that can be analogously interpreted as appending cells to a key diagram, albeit potentially dropping some cells in between each cell addition. I will also outline the main points of the rules bijective proof, and in the process hopefully illustrate the utility of understanding the rule from a diagrammatic perspective. Joint work with Sami Assaf. 
Fri Nov 22 
Special Events and Seminars3:30pm  Vincent Hall 20Mass Scale Image Analysis For Automated Plant Phenotyping and Classification via Machine Learning Riley O'Neill, University of St. Thomas Abstract:The capacity to quantify crop architecture and morphology is foundational to the development of higher yielding cultivars via hybridization and genetic engineering. However, at the mass scale required by the science, manual plant phenotyping with physical instruments is arduous, time consuming, subjective, and a leading cause of undergraduate burnout in the UMN plant genetics department. While the process has been slightly improved with manual image analysis, such is almost as time consuming and remains subject to human error. Thereby, in efforts to further expedite phenotyping processes, circumvent human error, and provide more detailed analyses, we aim to completely automate plant phenotyping processes for the UMN plant genetics department and beyond. Working from over 15,000 soybean plants, weve advanced robust image processing platforms for measuring petiole and stem length, leaf area, leaf shape via signature curves, and branch angles via energy minimization in 2D, and begun preliminary work at 3D reconstructions from 2D data for 3D branch angles and further analyses. After data extraction and verification, we plan to implement clustering algorithms and machine learning to automatically group plant phenotypes as well as conduct principal component analysis to assemble an allometry space and identify the primary genes of influence. 
Fri Nov 22 
AMAAZE3:30pm  Vincent Hall 20Mass Scale Image Analysis For Automated Plant Phenotyping and Classification via Machine Learning Riley O'Neill, University of St. Thomas Abstract:The capacity to quantify crop architecture and morphology is foundational to the development of higher yielding cultivars via hybridization and genetic engineering. However, at the mass scale required by the science, manual plant phenotyping with physical instruments is arduous, time consuming, subjective, and a leading cause of undergraduate burnout in the UMN plant genetics department. While the process has been slightly improved with manual image analysis, such is almost as time consuming and remains subject to human error. Thereby, in efforts to further expedite phenotyping processes, circumvent human error, and provide more detailed analyses, we aim to completely automate plant phenotyping processes for the UMN plant genetics department and beyond. Working from over 15,000 soybean plants, weve advanced robust image processing platforms for measuring petiole and stem length, leaf area, leaf shape via signature curves, and branch angles via energy minimization in 2D, and begun preliminary work at 3D reconstructions from 2D data for 3D branch angles and further analyses. After data extraction and verification, we plan to implement clustering algorithms and machine learning to automatically group plant phenotypes as well as conduct principal component analysis to assemble an allometry space and identify the primary genes of influence. 
Fri Nov 22 
Probability Seminar2:30pm  Vincent Hall 311Spherical spin glass models Eliran Subag, New York University Abstract:How many critical points does a smooth random function on a highdimensional space typically have at a given height? how are their distances distributed? what is the volume or geometry of the level sets? can we design efficient optimization algorithms for the random function? For the spherical spin glass models, those questions are closely related to the structure of the Gibbs measures, which have been extensively studied in physics since the 70s. I will start with an overview of the celebrated Parisi formula and ultrametricity property. I will then describe an alternative method to analyze the Gibbs measure using critical points, in the setting of the pure spherical models. Finally, I will explain how the latter can be extended to all spherical models, using another (soft) geometric approach, while at the same time making rigorous and generalizing the famous ThoulessAndersonPalmer approach from physics. 
Fri Nov 22 
Math Biology Seminar2:30pm  VinH 209Math Biology Seminar 
Fri Nov 22 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Nov 22 
Special Events and Seminars1:25pm  Vincent Hall 213"pAdic Cohomology, Exponential Sums, and Hypergeometric Functions TBA 
Fri Nov 22 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Machine Learning Problems at Target Mauricio Flores, Target Corporation Abstract:PhD and Master's students would likely benefit the most from this talk. There will be some discussion on opportunities at Target. The introduction of this talk will provide an overview of the AI sciences organization at Target and discuss summer internship opportunities. The remainder of the talk will overview the kinds of machine learning problems Target deals with, and dive into three such problems, in the fields of recommender systems and computer vision. Mauricio Flores received his PhD in Applied Mathematics from the University of Minnesota in 2018, under the supervision of Jeff Calder & Gilad Lerman. He is currently a Lead AI Scientist at Target, where he builds machine learning as well as computer vision models for visually compatible recommendations, and more recently, for damage detection in Targets distribution centers. 
Thu Nov 21 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Nov 21 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Nov 21 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar Erika Ordog, Duke University 
Thu Nov 21 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Geometry of degenerating CalabiYau manifolds Ruobing Zhang, Stony Brook Abstract:This talk concerns a family of "collapsing" Ricciflat Kähler manifolds, namely CalabiYau manifolds, converging to a lower dimensional limit, which develop singularities arising in various contexts such as metric Riemannian geometry, complex geometry and degenerating nonlinear equations. A primary aspect is to formulate how well behaved or badly behaved such spaces can be in terms of the recently developed regularity theory. Under the above framework, our next focus is on a longstanding fundamental problem which is to understand singularities of collapsing Ricciflat metrics along an algebraically degenerating family. We will give accurate characterizations of such metrics and explain possible generalizations. 
Thu Nov 21 
Topology Seminar7:00am  SkyboxLOWER (Legs + Butt) @ Skybox  Skybox Abstract:https://www.fitmetrix.io/webportal/schedulemobile/f9719b204914e911a97...(Legs%20%2B%20Butt)&dateRangeFrom=20191121T07%3A00%3A00&dateRangeTo=20191121T07%3A55%3A00&locationid=5854&classID=31918145 
Wed Nov 20 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Nov 20 
PDE Seminar3:35pm  Vincent Hall 570Effective Poisson equation of density functional theory at positive temperature Li Chen, MIT Abstract:Density functional theory (DFT) has been a very successful effective theory of manybody quantum mechanics. In particular, the KohnSham (KS) equations of DFT serve as an accurate model for the electron densities. The KS equations are a case of the SchrodingerPoisson equations whose electronelectron effective interaction potential only depends on the density of electrons. When the number of electrons are limited, the KS equation can be solved quickly by numerical method at temperature T = 0. Since physically interesting settings are at T > 0, we study the KS equations at positive temperature and give an iterative scheme to construct solutions. One important class of electronic structures described by the KS equations is a crystalline lattice. At positive temperature, we show that a local perturbation to a crystalline structure induces an electric field governed by the Poisson equation. The latter equation emerges as an effective equation of the KS equations. This is a joint work with Israel M. Sigal. 
Wed Nov 20 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Nov 19 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Nov 19 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Nov 19 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Nov 19 
Colloquium2:30pm  Vincent Hall 16Random matrix theory and supersymmetry techniques Tatyana Shcherbyna, Princeton University Abstract:Starting from the works of Erdos, Yau, Schlein with coauthors, the significant progress in understanding the universal behavior of many random graph and random matrix models were achieved. However for the random matrices with a spacial structure our understanding is still very limited. In this talk I am going to overview applications of another approach to the study of the local eigenvalues statistics in random matrix theory based on socalled supersymmetry techniques (SUSY) . SUSY approach is based on the representation of the determinant as an integral over the Grassmann (anticommuting) variables. Combining this representation with the representation of an inverse determinant as an integral over the Gaussian complex field, SUSY allows to obtain an integral representation for the main spectral characteristics of random matrices such as limiting density, correlation functions, the resolvent's elements, etc. This method is widely (and successfully) used in the physics literature and is potentially very powerful but the rigorous control of the integral representations, which can be obtained by this method, is quite difficult, and it requires powerful analytic and statistical mechanics tools. In this talk we will discuss some recent progress in application of SUSY to the analysis of local spectral characteristics of the prominent ensemble of random band matrices, i.e. random matrices whose entries become negligible if their distance from the main diagonal exceeds a certain parameter called the band width. 
Tue Nov 19 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Nov 19 
IMA Data Science Lab Seminar1:25pm  Lind 305Robust Representation for Graph Data Dongmian Zou, University of Minnesota, Twin Cities Abstract:Modern data are usually highdimensional with noise and corruption. A useful representation of data has to be robust and address the data structure. In this talk, I will first present a class of robust models called the scattering transform that can be used to generated features from graph data. In graph scattering transforms, the representation is generated in an unsupervised manner based on graph wavelets. It is approximately invariant to permutations and stable to signal or graph manipulations. Numerical results show that it works effectively for classification and community detection problems. Next, I will address how the structure of data can be found using autoencoders. Indeed, in the framework of autoencoders, graph scattering transform can be applied to the important task of graph generation. It shows stateoftheart performance in link prediction and can be used to generate molecular samples. 
Tue Nov 19 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Tue Nov 19 
Topology Seminar10:30am  SkyboxCORE @ Skybox  Skybox Abstract:https://www.fitmetrix.io/webportal/schedulemobile/f9719b204914e911a97... 
Mon Nov 18 
Student Number Theory Seminar3:35pm  Vincent Hall 1The CasselmanShalika Formula for GL_2 Emily Tibor Abstract:This talk will focus on the CasselmanShalika formula for GL_2 over a nonArchimedean local field, which is an explicit formula for the values of the spherical Whittaker function. A good amount of time will be dedicated to explaining the necessary background including Whittaker models and spherical vectors, which come together to form the spherical Whittaker function. We will then be ready to discuss the formula, Casselman's method of calculating it, and its significance. 
Mon Nov 18 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Scalable Algorithms for Datadriven Inverse and Learning Problems Tan BuiThanh, UTAustin Abstract:Inverse problems and uncertainty quantification (UQ) are pervasive in scientific To address the first challenge, we have developed parallel highorder (hybridized) discontinuous Galerkin methods to discretize complex forward PDEs. To address the second challenge, we have developed various approaches from model reduction to advanced Markov chain Monte Carlo methods to effectively explore high dimensional parameter spaces to compute posterior statistics. To address the last challenge, we have developed a randomized misfit approach that uncovers the interplay between the JohnsonLindenstrauss and the Morozov's discrepancy principle to significantly reduce the dimension of the data without compromising the quality of the inverse solutions. In this talk we selectively present scalable and rigorous approaches to tackle these challenges for PDEgoverned Bayesian inverse problems. Various numerical results for simple to complex PDEs will be presented to verify our algorithms and theoretical findings. If time permits, we will present our recent work on scientific machine learning for inverse and learning problems. 
Mon Nov 18 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Nov 18 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Nov 18 
Topology Seminar2:30pm  Ford Hall 110Topology Seminar TBA 
Mon Nov 18 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Nov 15 
MCFAM Seminar5:30pm  Vincent Hall 16Data Science in the Life Insurance Industry Gary Hatfield, Securian/University of Minnesota Abstract:Data Scientist has emerged as one of the hottest and most talked about jobs in the world today. In my talk, I will provide an overview of how data science has emerged in the insurance industry. I will give some examples of how data science is being applied in life insurance and describe how the Actuarial profession is adapting. Bio: https://mcfam.dl.umn.edu/people/garyhatfield 
Fri Nov 15 
Combinatorics Seminar3:30pm  Vincent Hall 570Simplicial generation of Chow rings of matroids Chris Eur, UC Berkeley Abstract:Matroids are combinatorial objects that capture the essence of linear independence. We first give a gentle introduction to the recent breakthrough in matroid theory, the Hodge theory of matroids, developed by Adiprasito, Huh, and Katz. By combining two prominent recent approaches to matroids, tropical geometric and Lie/Coxeter theoretic, we give a new presentation for the Chow ring of a matroid that further tightens the interaction between combinatorics and geometry of matroids. We discuss various applications, including a simplified proof of the main portion of the Hodge theory of matroids. This is joint work with Spencer Backman and Connor Simpson. 
Fri Nov 15 
Probability Seminar2:30pm  Vincent Hall 311Joint seminar in math biology and probability: Mathematical Modelling in Immunotherapy of Melanoma Anna Kraut, Bonn Abstract:Mathematical models can support biomedical research through identification of key mechanisms, validation of experiments, and simulation of new therapeutic approaches. We investigate the evolution of melanomas under adoptive cell transfer therapy with cytotoxic Tcells. It was shown in experiments that phenotypic plasticity, more precisely an inflammationinduced, reversible dedifferentiation, is an important escape mechanism for the tumor. Recently, the effects of possible mutation to a permanently resistant genotype were studied by introducing knockout melanoma cells into the wildtype tumor. We use a stochastic individualbased Markov process to describe the evolution of the tumor under various therapeutic approaches. It is an extension of the model introduced in the paper of Baar et al in 2016 and further includes the effects of Tcell exhaustion and some limited spatial component which results in additional nonlinearities. The model is implemented as a hybrid algorithm that combines Gillespietype stochastic calculations and a deterministic approximation to speed up simulations while keeping the effects of random events. Numerical simulations confirm the resistance to therapy via phenotypic switching as well as genotypic mutation. Tcell exhaustion is identified as an important mechanism that is crucial in fitting the model to the experimental data. We gain further insights into how originally unfit knockout cells can accumulate under therapy, shield the wild type cells from the Tcells, and thus cause an earlier relapse. Going beyond the experiment, the possibility of naturally occurring rare mutations, in contrast to artificially introduced knockout cells, is explored in simulations and produces the same effects. Thus, the clinical relevance of the experimental findings can be confirmed. 
Fri Nov 15 
Math Biology Seminar2:30pm  Vincent Hall 311Joint seminar in math biology and probability: Mathematical Modelling in Immunotherapy of Melanoma Anna Kraut, Bonn Abstract:Mathematical models can support biomedical research through identification of key mechanisms, validation of experiments, and simulation of new therapeutic approaches. We investigate the evolution of melanomas under adoptive cell transfer therapy with cytotoxic Tcells. It was shown in experiments that phenotypic plasticity, more precisely an inflammationinduced, reversible dedifferentiation, is an important escape mechanism for the tumor. Recently, the effects of possible mutation to a permanently resistant genotype were studied by introducing knockout melanoma cells into the wildtype tumor. We use a stochastic individualbased Markov process to describe the evolution of the tumor under various therapeutic approaches. It is an extension of the model introduced in the paper of Baar et al in 2016 and further includes the effects of Tcell exhaustion and some limited spatial component which results in additional nonlinearities. The model is implemented as a hybrid algorithm that combines Gillespietype stochastic calculations and a deterministic approximation to speed up simulations while keeping the effects of random events. Numerical simulations confirm the resistance to therapy via phenotypic switching as well as genotypic mutation. Tcell exhaustion is identified as an important mechanism that is crucial in fitting the model to the experimental data. We gain further insights into how originally unfit knockout cells can accumulate under therapy, shield the wild type cells from the Tcells, and thus cause an earlier relapse. Going beyond the experiment, the possibility of naturally occurring rare mutations, in contrast to artificially introduced knockout cells, is explored in simulations and produces the same effects. Thus, the clinical relevance of the experimental findings can be confirmed. 
Fri Nov 15 
Dynamical Systems2:30pm  Vincent Hall 20The mathematics of taffy pulling JeanLuc Thiffeault, University of Wisconsin Abstract:Taffy is a type of candy made by repeated 'pulling' (stretching andfolding) a mass of heated sugar. The purpose of pulling is to get air 
Fri Nov 15 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Nov 15 
Special Events and Seminars1:25pm  Vincent Hall 213"pAdic Cohomology, Exponential Sums, and Hypergeometric Functions TBA 
Fri Nov 15 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Pipelines, Graphs, and the Language of Shopping: Architecting Next Gen Machine Learning Capabilities for Retail Jonah White, Best Buy Abstract:This talk will highlight the evolution of building out a data science capability in a retail environment as well as explore cuttingedge developments in constructing machine learning pipelines in the cloud, emerging advancements in timeseries forecasting, applications of GPU accelerated graph processing for entity resolution, and how were adapting the latest research in language models to translate the language of shopping for the ultimate personalized experience 
Thu Nov 14 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Nov 14 
Colloquium3:35pm  Vincent Hall 16$p$adic estimates for exponential sums on curves Joe KramerMiller, UC Irvine Abstract:A central problem in number theory is that of finding rational or integer solutions to systems of polynomials in several variables. This leads one naturally to the slightly easier problems of finding solutions modulo a prime $p$. Using a discrete analogue of the Fourier transformation, this modulo $p$ problem can be reformulated in terms of exponential sums. We will discuss $p$adic properties of such exponential sums in the case of higher genus curves as well as connections to complex differential equations. 
Thu Nov 14 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar Gennady Lyubeznik, University of Minnesota 
Thu Nov 14 
Colloquium2:30pm  Vincent Hall 16Applications of Frobenius beyond prime characteristic. Daniel Hernández, Univ. of Kansas Abstract:Abstract: Recall that the Frobenius morphism is simply the map sending an element in a ring of prime characteristic $p>0$  say, a polynomial with coefficients in a finite field  to its $p$th power. Though simple to define, Frobenius has proven to be a useful and effective tool in algebraic geometry, representation theory, number theory, and commutative algebra. Furthermore, and remarkably, some of the most interesting applications of Frobenius are to the study of objects defined over the complex numbers, and more generally, over a field of characteristic zero! In this talk, we will discuss some of these applications, with an eye towards classical singularity theory and birational algebraic geometry, both over the complex numbers. 
Thu Nov 14 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Nov 13 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Nov 13 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Counting points and varieties and Malle's conjecture Andy Odesky, University of Michigan 
Wed Nov 13 
PDE Seminar3:30pm  Vincent Hall 570Serrin Lecture  Localization for the AndersonBernoulli model on the integer lattice Charles Smart, University of Chicago Abstract:I will give a brief mathematical introduction to Anderson localization followed by a discussion of my recent work with Jian ding. In our work we establish localization near the edge for the Anderson Bernoulli model on the two dimensional lattice. Our proof follows the program of BourgainKenig and uses a new unique continuation result inspired by BuhovskyLogunovMalinnikovaSodin. I will also discuss recent work of by Li and Zhang on the three dimensional case. 
Tue Nov 12 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Nov 12 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Nov 12 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Nov 12 
Colloquium2:30pm  Vincent Hall 16Unraveling Local Cohomology Emily Witt, Univ. of Kansas Abstract:Local cohomology modules are fundamental tools in commutative algebra, due to the algebraic and geometric information they carry. For instance, they can help determine the number of equations necessary to define an affine variety. Unfortunately, however, the application of local cohomology is limited by the fact that these modules are typically very large (e.g., not finitely generated), and can be difficult to determine explicitly. In this talk, we discuss new techniques developed to understand the structure of local cohomology (e.g., coming from invariant theory). We also describe recentlydiscovered "connectedness properties" of spectra that local cohomology encodes. 
Tue Nov 12 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Nov 12 
IMA Data Science Lab Seminar1:25pm  Lind 305Latent Factor Models for Largescale Data Xiaoou Li, University of Minnesota, Twin Cities Abstract:Latent factor models are widely used to measure unobserved latent traits in social and behavioral sciences, including psychology, education, and marketing. Motivated by the applications of latent factor models to largescale measurements which consist of many manifest variables (e.g. test items) and a large sample size, we study the properties of latent factor models under an asymptotic setting where both the number of manifest variables and the sample size grows to infinity. In this talk, I will introduce generalized latent factor models under exploratory and confirmatory settings. For the exploratory setting, we propose a constrained joint maximum likelihood approach for model estimation and investigate its theoretical properties. For the confirmatory setting, we study how the design information affects the identifiability and estimability of the model, and propose a rateoptimal estimator when the model is identifiable. The estimators can be efficiently computed through parallel computing. Our results provide insights on the design of largescale measurement and have important implications on measurement validity. 
Tue Nov 12 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Nov 11 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Nov 11 
Student Number Theory Seminar3:35pm  Vincent Hall 1Introduction to RankinSelberg Method Shengmei An Abstract:RankinSelberg method has been one of the most powerful techniques for studying the Langlands program. In this talk, we will start with the original simplest example of the RankinSelberg method, and then come to a more general case of the RankinSelberg method on GL_m*GL_n where we can reduce the global integral to the more accessible lovely local integrals so that we can establish some of the important analytic properties of the Lfunctions. 
Mon Nov 11 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Nov 11 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Nov 11 
Topology Seminar2:30pm  Ford Hall 110Cochain models for the unit group of a differential graded algebra Tyler Lawson, University of Minnesota Abstract:Abstract not available. 
Mon Nov 11 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Nov 08 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Nov 08 
Combinatorics Seminar3:30pm  Vincent Hall 570Combinatorics via Deligne Categories Chris Ryba, MIT Abstract:The Deligne category Rep(S_t) can be thought of as "interpolating" the representation categories of symmetric groups. After describing this category, I will explain how a calculation in the Deligne category can be used to prove stability properties of permutation patterns within conjugacy classes (joint with Christian Gaetz). 
Fri Nov 08 
Probability Seminar2:30pm  Vincent Hall 311"Robust Synchronization via Cycle Consistency Inference Yunpeng Shi, UMN Abstract:We propose a strategy for improving the existing methods for solving synchronization problems that arise from various computer vision tasks. Specifically, our strategy identifies severely corrupted relative measurements based on cycle consistency information. To the best of our knowledge, this paper provides the first exact recovery guarantees using cycle consistency information. This result holds for a noiseless but corrupted setting as long as the ratio of corrupted cycles per edge is sufficiently small. It further guarantees linear convergence to the desired solution. We also establish stability of the proposed algorithm to subGaussian noise. 
Fri Nov 08 
Math Biology Seminar2:30pm  Vincent Hall 311Joint seminar in math biology and probability: Mathematical Modelling in Immunotherapy of Melanoma Anna Kraut, Bonn Abstract:Mathematical models can support biomedical research through identification of key mechanisms, validation of experiments, and simulation of new therapeutic approaches. We investigate the evolution of melanomas under adoptive cell transfer therapy with cytotoxic Tcells. It was shown in experiments that phenotypic plasticity, more precisely an inflammationinduced, reversible dedifferentiation, is an important escape mechanism for the tumor. Recently, the effects of possible mutation to a permanently resistant genotype were studied by introducing knockout melanoma cells into the wildtype tumor. We use a stochastic individualbased Markov process to describe the evolution of the tumor under various therapeutic approaches. It is an extension of the model introduced in the paper of Baar et al in 2016 and further includes the effects of Tcell exhaustion and some limited spatial component which results in additional nonlinearities. The model is implemented as a hybrid algorithm that combines Gillespietype stochastic calculations and a deterministic approximation to speed up simulations while keeping the effects of random events. Numerical simulations confirm the resistance to therapy via phenotypic switching as well as genotypic mutation. Tcell exhaustion is identified as an important mechanism that is crucial in fitting the model to the experimental data. We gain further insights into how originally unfit knockout cells can accumulate under therapy, shield the wild type cells from the Tcells, and thus cause an earlier relapse. Going beyond the experiment, the possibility of naturally occurring rare mutations, in contrast to artificially introduced knockout cells, is explored in simulations and produces the same effects. Thus, the clinical relevance of the experimental findings can be confirmed. 
Fri Nov 08 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Nov 08 
Special Events and Seminars1:25pm  Vincent Hall 213"pAdic Cohomology, Exponential Sums, and Hypergeometric Functions Steven Sperber 
Thu Nov 07 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Nov 07 
Colloquium3:35pm  Vincent Hall 16Eisenstein Series on Loop Groups and their Metaplectic Covers Manish Patnaik, University of Alberta Abstract:Both the LanglandsShahidi method of studying automorphic Lfunctions and approach via the theory of Weyl group multiple Dirichlet series to studying moments of Lfunctions now require new classes of groups with which to work. In this talk, I will explain our progress on extending these techniques to certain infinitedimensional KacMoody groups, namely loop groups (and their metaplectic covers). Of note in our work is the presence of two quite different types of Eisenstein series that exist on the same group and which need to be considered in conjunction with one other. This is a report on joint work in progress with H. Garland, S.D. Miller, and A. Puskas. 
Thu Nov 07 
Commutative Algebra Seminar2:30pm  Vincent Hall 209The spectral sequence of a filtered complex Gennady Lyubeznik, University of Minnesota Abstract:This is the third of a series of three talks on the spectral sequence of a filtered complex. This material is by now classical and is an important part of homological algebra. The main difficulty in dealing with spectral sequences is that there are a lot of indexes involved and this is a considerable obstacle to understanding what is going on. The goal of these talks is to present this material, including most proofs, in an accessible manner. 
Thu Nov 07 
Colloquium2:30pm  Vincent Hall 16On various questions (and answers) in Highdimensional probability Galyna Livshyts, Georgia Tech Abstract:In this talk, several topics from Highdimensional probability shall be discussed. This fascinating area is rich in beautiful problems, and several easytostate questions will be outlined. Further, some connections between them will be explained throughout the talk. I shall discuss several directions of my research. One direction is invertibility properties of inhomogeneous random matrices: I will present sharp estimates on the small ball behavior of the smallest singular value of a very general ensemble of random matrices, and will briefly explain the new tools I developed in order to obtain these estimates. Another direction is isoperimetrictype inequalities in highdimensional probability. Such inequalities are intimately tied with concentration properties of probability measures. Among other results, I will present a refinement of the concavity properties of the standard gaussian measure in an ndimensional euclidean space, under certain structural assumptions, such as symmetry. This result constitutes the best known to date estimate in the direction of the conjecture of Gardner and Zvavitch from 2007. The above topics will occupy most of the time of the presentation. In addition, I shall briefly mention other directions of my research, including noisesensitivity estimates for convex sets, or, in other words, upper bounds on perimeters of convex sets with respect to various classes of probability distributions. If time permits, I will discuss my other results, such as small ball estimates for random vectors with independent coordinates, and partial progress towards LeviHadwiger illumination conjecture for convex sets in high dimensions. 
Thu Nov 07 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Nov 06 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Nov 06 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Wed Nov 06 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213The automorphic heat kernel from a geometric perspective Amy DeCelles, St. Thomas 
Tue Nov 05 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Nov 05 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Nov 05 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Nov 05 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Nov 05 
IMA Data Science Lab Seminar1:25pm  Lind 305Topics in Sparse Recovery via Constrained Optimization: Least Sparsity, Solution Uniqueness, and Constrained Exact Recovery Seyedahmad Mousavi, University of Minnesota, Twin Cities Abstract:Sparse recovery finds numerous applications in different areas, for example, engineering, computer science, business, applied mathematics, and statistics. Sparse recovery is often formulated as relatively largescale and challenging constrained (convex or nonconvex) optimization problems. Constraints are ubiquitous and important in many applications of sparse recovery, but they make analysis and computation nontrivial and require novel techniques to handle them. The goal of this talk is to present numerical and analytical techniques for constrained sparse recovery using convex analysis and optimization tools. Three topics are investigated in the realm of constrained sparse recovery. First, we analyze quantitative adverse properties of different $p$normbased optimization problems with $p>1$, such as generalized basis pursuit, basis pursuit denoising, ridge regression, and elastic net. We show that their optimal solutions are least sparse for almost all measurement matrices and measurement vectors. Second, we study the solution uniqueness of an individual feasible vector of a class of convex optimization problems involving convex piecewise affine functions and subject to general polyhedral constraints. We apply these solution uniqueness results to a broad class of $\ell_1$minimization problems in constrained sparse optimization, such as basis pursuit, LASSO, and polyhedral gauge recovery. Third, we propose a constrained matching pursuit algorithm for constrained sparse recovery and develop uniform conditions for exact support and vector recovery on constraint sets. The exact recovery via this algorithm not only depends on a measurement matrix but also critically relies on a constraint set. Hence, we identify an important class of constraint sets, called coordinate projection admissible. We then use the conic hull structure of these sets together with constrained optimization techniques to establish sufficient conditions for uniform exact recovery via this algorithm on coordinate projection admissible sets. These conditions are expressed in terms of the restricted isometrylike and the restricted orthogonalitylike constants 
Tue Nov 05 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Nov 04 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Nov 04 
Student Number Theory Seminar3:35pm  Vincent Hall 1RankinSelberg Method May Shengmei 
Mon Nov 04 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied differential geometry and harmonic analysis in deep learning regularization Wei Zhu, Duke University Abstract:Deep neural networks (DNNs) have revolutionized machine learning by gradually replacing the traditional modelbased algorithms with datadriven methods. While DNNs have proved very successful when large training sets are available, they typically have two shortcomings: First, when the training data are scarce, DNNs tend to suffer from overfitting. Second, the generalization ability of overparameterized DNNs still remains a mystery. In this talk, I will discuss two recent works to inject the modeling flavor back into deep learning to improve the generalization performance and interpretability of the DNN model. This is accomplished by DNN regularization through applied differential geometry and harmonic analysis. In the first part of the talk, I will explain how to improve the regularity of the DNN representation by enforcing a lowdimensionality constraint on the datafeature concatenation manifold. In the second part, I will discuss how to impose scaleequivariance in network representation by conducting joint convolutions across the space and the scaling group. The stability of the equivariant representation to nuisance input deformation is also proved under mild assumptions on the FourierBessel norm of filter expansion coefficients. 
Mon Nov 04 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Nov 04 
Topology Seminar2:30pm  Ford Hall 110Topology Seminar TBA 
Mon Nov 04 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Nov 01 
MCFAM Seminar5:30pm  Vincent Hall 16Extrapolative Expectations, Financial Frictions, and Asset Prices Yao Deng, University of Minnesota Abstract:I study how extrapolative expectations affect corporate real and financial activities and asset prices. Empirically, high misperception on earnings growth, a measure constructed to proxy for extrapolation, is associated with an increase in investment, debt issuance, equity issuance, and firmlevel bond and stock prices in the shortterm, but predicts a decline in all these activities and prices in the longterm. These patterns are more pronounced among small and financially constrained firms. Theoretically, I build a dynamic model with extrapolative expectations and financial frictions, and show that the interaction of these two frictions is crucial to explain the empirical findings. Intuitively, after a sequence of favorable shocks, agents extrapolate and become overoptimistic about future productivities. Firms invest and borrow more in the shortterm. Lower perceived default probability improves financing conditions, further increasing investment and borrowing. Future realizations turn out worse than expected, making real and financial activities and asset prices subject to predictable reversals in the longterm.Bio: https://carlsonschool.umn.edu/faculty/yaodeng 
Fri Nov 01 
Combinatorics Seminar3:30pm  Vincent Hall 570Combinatorics Seminar Dongkwan Kim, UMN Abstract:For a Coxeter group W, a Wgraph is a graph which produces a nice basis of the corresponding representation of W and also describes the action of W on the basis elements. Even when W is finite and its irreducible characters are known, Wgraphs are still useful for understanding representations of W. In this talk, I will talk about Wgraphs when W is an (extended) affine symmetric group, especially when these graphs are associated with tworow partitions. Also I will discuss the connection between them and Lusztigs periodic Wgraph. This work is joint with Pavlo Pylyavskyy. 
Fri Nov 01 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar 
Fri Nov 01 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Nov 01 
Special Events and Seminars1:25pm  Vincent Hall 213pAdic Banach Spaces and Completely Continuous Endomorphisms Steven Sperber 
Thu Oct 31 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Oct 31 
Colloquium3:35pm  Vincent Hall 16Differential operators on invariant rings Anurag Singh, University of Utah Abstract:Work of Levasseur and Stafford describes the rings of differential operators on various classical invariant rings of characteristic zero; in each of these cases, the differential operators form a simple ring. Towards an attack on the simplicity of rings of differential operators on invariant rings of reductive groups over the complex numbers, Smith and Van den Bergh asked if reduction modulo p works for differential operators in this context. In joint work with Jack Jeffries, we establish that this is not the case for various classical groups. 
Thu Oct 31 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Spectral sequences Gennady Lyubeznik, University of Minnesota Abstract:This is the first of a series of three talks on the spectral sequence of a filtered complex. 
Thu Oct 31 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Oct 30 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Oct 30 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Wed Oct 30 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Oct 29 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Oct 29 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Oct 29 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Oct 29 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Oct 29 
IMA Data Science Lab Seminar1:25pm  Lind 305Highly Likely Clusterable Data With No Cluster Mimi Boutin, Purdue University Abstract:Data generated as part of a reallife experiment is often quite organized. So much so that, in many cases, projecting the data onto a random line has a high probability of uncovering a clear division of the data into two wellseparated groups. In other words, the data can be clustered with a high probability of success using a hyperplane whose normal vector direction is picked at random. We call such data ``highly likely clusterable. The clusters obtained in this fashion often do not seem compatible with a cluster structure in the original space. In fact, the data in the original space may not contain any cluster at all. This talk is about this surprising phenomenon. We will discuss empirical ways to detect it as well as how to exploit it to cluster datasets, especially datasets consisting of a small number of points in a highdimensional space. We will also present a possible mathematical model that would explain this observed phenomenon. This is joint work with Alden Bradford (Purdue Math), Sangchun Han (Purdue ECE, now at Google) and Tarun Yellamraju (Purdue ECE, now at Qualcomm). Mireille (Mimi) Boutin graduated with a bachelors degree in PhysicsMathematics from the University of Montreal. She received the Ph.D. degree in Mathematics from the University of Minnesota under the direction of Peter J. Olver. She joined Purdue University after a postdoctorate with David Mumford, David Cooper, and Ben Kimia at Brown University, Rhode Island, followed by a postdoctorate with Stefan Muller at the Max Plank Institute for Mathematics in the Sciences in Leipzig, Germany. She is currently an Associate Professor in the School of Electrical and Computer Engineering, with a courtesy appointment in the Department of Mathematics. Her research is in the area of signal processing, machine learning, and applied mathematics. She is a threetime recipient of Purdues Seed for Success Award. She is also a recipient of the Eta Kappa Nu Outstanding Faculty Award, the Eta Kappa Nu Outstanding Teaching Award and the Wilfred Duke Hesselberth Award for Teaching Excellence. 
Tue Oct 29 
Climate Seminar11:15am  Vincent Hall 570Convergence and Equilibrium for Stochastic Models of Ecological Disturbances James Broda, Bowdoin College 
Mon Oct 28 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Oct 28 
Student Number Theory Seminar3:35pm  Vincent Hall 1"Part 2: Representation Stability, Étale Cohomology and Combinatorics of Configuration Spaces over Finite Fields" David DeMark Abstract:After introducing the theory of FImodules in 2012, the collaborative unit consisting of Thomas Church, Jordan Ellenberg and Benson Farb applied their framework to asymptotically stable counting problems in a certain classes of FIvarieties over finite fields in their 2013 paper Representation stability in cohomology and asymptotics for families of varieties over finite fields. The paper serves as a proofofconcept, unifying a number of previouslyknown combinatorial results. The key to their method is the GrothendieckLefschetz fixedpoint theorem with twisted statistics, which relates the rational cohomology of an algebraic variety over the complex numbers with the trace of the Frobenius map applied to the étale cohomology with coefficients in an $\ell$adic sheaf of that variety over a finite field. In this talk, we shall introduce the GrothendieckLefschetz formula and its associated machinery as well as FImodules and representation stability, then use these ideas to give an exposition of some results of Church, Ellenberg and Farb as they relate to configuration spaces and the braid group. 
Mon Oct 28 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Oct 28 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Oct 28 
Topology Seminar2:30pm  Ford Hall 110Compactifying the étale topos Elden Elmanto, Harvard University Abstract:The speaker has long feared the technicalities and intricacies of equivariant stable homotopy theory. Fortunately, beginning with the work of Glasman, major simplification on the foundations of the subject has been made (cf. the work of AyalaMazelGeeRozenblyum, NikolausScholze and the Barwick school). We offer another perspective (that the speaker has a chance of understanding) on equivariant stable homotopy theory, at least for the group C_2, via algebraic geometry. We view it as a way to remedy an infamous annoyance: the 2étale cohomological dimension of the field of real numbers is infinite. We do this by identifying the genuine C_2spectra with a category of motives based on Real algebraic geometry ala Scheiderer. This is joint work with Jay Shah. 
Mon Oct 28 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Oct 25 
MCFAM Seminar5:30pm  Vincent Hall 16Mortgage Prepayment Behavior Messan Edorh and Bo Li, US Bank Abstract:According to the US Census Bureau, homeownership rates peaked during the first quarter of 2005 at 69.1% but fell to just 63.8% in the fourth quarter of 2015, a year when residential mortgage debt outstanding was still above ten trilliondollar mark and mortgage origination was about $1.7T. Mortgage Back Security (MBS) originations have continued to experience a steady growth attracting investors, servicers, insurers, lenders, and GSEs (Government Sponsored Enterprises). In contrary, MBS market presented various financial risks including prepayment from the homeowners  be that voluntary or involuntary. To manage the risks presented by the borrowers, modeling prepayment behavior is critical in the work banks do. Four fundamental components of mortgage prepayment activity will be examined in this presentation. 
Fri Oct 25 
Combinatorics Seminar3:30pm  Vincent Hall 570Combinatorial Methods for Integrable Systems Nick Ovenhouse. Abstract:An integrable Hamiltonian system is a dynamical system with "enough conserved quantities" to guarantee that it can, in principle, be solved, or "integrated". I will give some basic definitions of Poisson algebras and what it means to be integrable in this context. I will then show, by way of an example (namely the "pentagram map"), how some combinatorial techniques using weighted directed graphs can be used to model the system and demonstrate its integrability. This method also hints at connections with cluster algebras and Postnikov's constructions related to stratifications of the positive Grassmannian. Time permitting, I will also discuss recent work generalizing this example. 
Fri Oct 25 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar Kevin Leder, UMN 
Fri Oct 25 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Oct 25 
Special Events and Seminars1:25pm  Vincent Hall 213"pAdic Cohomology, Exponential Sums, and Hypergeometric Functions TBA 
Fri Oct 25 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Gamma Guidance  The Mathematics Applied to a Launch Vehicle Gary Green, The Aerospace Corporation Abstract:The Boeing Inertial Upper Stage (IUS) launch vehicle was used to launch spacecraft from 1982 until 2004. The Gamma Guidance algorithm was used on board the IUS to select the ignition times, durations, and directions of engine firings. I will discuss the mathematics employed in Gamma Guidance as well as collateral onboard ;processes in order to illuminate how mathematics is applied in the launch setting. Dr. Gary Green holds mathematics degrees from the Universities of Idaho, Michigan State, and Pennsylvania State. He taught mathematics at California State College Stanislaus before joining the Aerospace Corporation (www.aerospace.org), where he served as an applied mathematician and systems engineer in several capacities: employing numerical analysis to model launch vehicles, overseeing algorithm and software development for space systems, evaluating space system performance, and analyzing threats against space systems. 
Thu Oct 24 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Oct 24 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Oct 24 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Spectral Sequences Gennady Lyubeznik, University of Minnesota Abstract:This is the first of a series of three talks on the spectral sequence of a filtered complex. 
Thu Oct 24 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Oct 23 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Oct 23 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Wed Oct 23 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Oct 22 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Oct 22 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Oct 22 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Oct 22 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Oct 22 
IMA Data Science Lab Seminar1:25pm  Lind 305Convergence Rates and Semiconvexity Estimates for the Continuum Limit of Nondominated Sorting Brendan Cook, University of Minnesota, Twin Cities Abstract:Multiobjective optimization problems are ubiquitous in science and engineering contexts, and nondominated sorting is a sorting process fundamental to multiobjective optimization. Recently proposed approaches to nondominated sorting exploit an underlying PDE that arises in the continuum limit. The need for theoretical guarantees for nondominated sorting algorithms motivates the problem of finding rates of convergence for the continuum limit. In this talk I will introduce PDE techniques from the theory of viscosity solutions and show how they can be used to solve this problem. Furthermore, I will show how semiconvexity estimates can be used to bolster convergence rates, and discuss approaches to obtaining semiconvexity estimates. This talk is intended to be entirely selfcontained, so no prior knowledge of PDE will be assumed. 
Tue Oct 22 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Oct 21 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Oct 21 
Student Number Theory Seminar3:35pm  Vincent Hall 1"Representation Stability, Étale Cohomology and Combinatorics of Configuration Spaces over Finite Fields" David DeMark Abstract:After introducing the theory of FImodules in 2012, the collaborative unit consisting of Thomas Church, Jordan Ellenberg and Benson Farb applied their framework to asymptotically stable counting problems in a certain classes of FIvarieties over finite fields in their 2013 paper Representation stability in cohomology and asymptotics for families of varieties over finite fields. The paper serves as a proofofconcept, unifying a number of previouslyknown combinatorial results. The key to their method is the GrothendieckLefschetz fixedpoint theorem with twisted statistics, which relates the rational cohomology of an algebraic variety over the complex numbers with the trace of the Frobenius map applied to the étale cohomology with coefficients in an $\ell$adic sheaf of that variety over a finite field. In this talk, we shall introduce the GrothendieckLefschetz formula and its associated machinery as well as FImodules and representation stability, then use these ideas to give an exposition of some results of Church, Ellenberg and Farb as they relate to configuration spaces and the braid group. 
Mon Oct 21 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Oct 21 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Oct 21 
Topology Seminar2:30pm  Ford Hall 110Descent properties of topological Hochschild homology Liam Keenan, University of Minnesota Abstract:Algebraic Ktheory is an extremely rich but notoriously difficult invariant to compute. In order to make calculations tractible, topological Hochschild homology and topological cyclic homology were introduced, along with the Dennis and cyclotomic trace maps. A natural question to consider is whether or not these invariants are sheaves for various topologies arising in algebraic geometry. In fact, it turns out that topological Hochschild homology is a sheaf for the fpqc topology on connective commutative ring spectra. In this talk, I plan to introduce the language necessary and sketch the argument of this result. 
Mon Oct 21 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Oct 18 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Oct 18 
Combinatorics Seminar3:30pm  Vincent Hall 570Combinatorics Seminar 
Fri Oct 18 
Probability Seminar2:30pm  Vincent Hall 311Rare events in the spectrum of random matrices Kevin Leder, UMN Abstract:In this talk I will consider extreme behavior of the extremal eigenvalues of white Wishart matrices, which play an important role in multivariate analysis. I will focus on the case when the dimension of the feature p is much larger than or comparable to the number of observations n, a common situation in modern data analysis. I will discuss asymptotic approximations for the tail probabilities of the extremal eigenvalues. In addition, I will discuss the construction of an efficient Monte Carlo importance sampling algorithm to estimate the tail probabilities. Simulation results show that our method has the best performance among known approximation approaches, and furthermore provides an efficient and accurate way for evaluating the tail probabilities in practice. Based on joint work with Tiefieng Jiang and Gongjun Xu. 
Fri Oct 18 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Oct 18 
Special Events and Seminars1:25pm  Vincent Hall 213Trace Formula, continued Steven Sperber, University of Minnesota 
Thu Oct 17 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Oct 17 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Oct 17 
Colloquium3:35pm  Vincent Hall 16Hopf monoids relative to a hyperplane arrangement Marcelo Aguiar, Cornell University Abstract:The talk is based on recent and ongoing work with Swapneel 
Thu Oct 17 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar Rebecca R.G., George Mason University 
Thu Oct 17 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Oct 16 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Oct 16 
PDE Seminar3:35pm  Vincent Hall 570Optimal local wellposedness for the derivative nonlinear Schrodinger's equation Yu Deng, University of Southern California Abstract:In joint work with Andrea Nahmod and Haitian Yue, we prove local wellposedness for the derivative nonlinear Schrodinger's equation in FourierLebesgue space which has the same scaling as H^s for any s>0. This closes the gap left open by the work of GrunrockHerr where s>1/4. Here there is no trilinear estimate in any standard function space, instead we will construct the solution in a nonlinear submanifold (of a function space) by exploiting its structure. This is somehow inspired by the theory of paracontrolled distributions that Gubinelli et al. developed for stochastic PDEs, but our arguments are purely deterministic. 
Wed Oct 16 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Oct 15 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Oct 15 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Oct 15 
Dynamical Systems2:30pm  Vincent Hall 209Forecasting U.S. elections with compartmental models of infection Alexandria Volkening, Northwestern University Abstract:U.S. election forecasting involves polling likely voters, making assumptions about voter turnout, and accounting for various features such as state demographics and voting history. While political elections in the United States are decided at the state level, errors in forecasting are correlated between states. With the goal of shedding light on the forecasting process and exploring how states influence each other, we develop a framework for forecasting elections in the U.S. from the perspective of dynamical systems. Through a simple approach that borrows ideas from epidemiology, we show how to combine a compartmental model with public polling data from HuffPost and RealClearPolitics to forecast gubernatorial, senatorial, and presidential elections at the state level. Our results for the 2012 and 2016 U.S. races are largely in agreement with those of popular pollsters, and we use our new model to explore how subjective choices about uncertainty impact results. We conclude by comparing our forecasts for the senatorial and gubernatorial races in the U.S. midterm elections of 6 November 2018 with those of popular pollsters. This is joint work with Daniel Linder (Augusta Univ.), Mason Porter (UCLA), and Grzegorz Rempala (Ohio State Univ.) 
Tue Oct 15 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Oct 15 
IMA Data Science Lab Seminar12:30pm  Lind 305Simple Approaches to Complicated Data Analysis Deanna Needell, University of California, Los Angeles Abstract:Recent advances in technology have led to a monumental increase in largescale data across many platforms. One mathematical model that has gained a lot of recent attention is the use of sparsity. Sparsity captures the idea that high dimensional signals often contain a very small amount of intrinsic information. Using this notion, one may design efficient lowdimensional representations of largescale data as well as robust reconstruction methods for those representations. Binary, or onebit, representations of data for example, arise naturally in many applications, and are appealing in both hardware implementations and algorithm design. In this talk, we provide a brief background to sparsity and 1bit measurements, and present new results on the problem of data classification with low computation and resource costs. We illustrate the utility of the proposed approach on recently acquired data about Lyme disease. 
Tue Oct 15 
Climate Seminar11:15am  Vincent Hall 570Climate and NonSmooth Dynamics Cameron Thieme, School of Mathematics 
Mon Oct 14 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Oct 14 
Student Number Theory Seminar3:35pm  Vincent Hall 1Arithmetic Speculation on a Combinatorial Lemma Eric Stuckey Abstract:Reflection groups are an object in classical geometry with deep connections to Lie theory, representation theory, algebraic geometry, invariant theory, and combinatorics. The first half of the talk will give a quick introduction to various flavors of reflection groups. In the second half of the talk I will state a lemma about a restricted class of reflection groups, and discuss an idea for how incorporating cyclotomic fields may allow us to remove that restriction. 
Mon Oct 14 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Oct 14 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Oct 14 
Topology Seminar2:30pm  Ford Hall 110Second order terms in arithmetic statistics Craig Westerland, University of Minnesota Abstract:The machinery of the Weil conjectures often allows us to relate the singular cohomology of the complex points of a scheme to the cardinality of its set of points over a finite field. When we apply these methods to a moduli scheme, we obtain an enumeration of the objects the moduli parameterizes. It's rare that we can actually fully compute the cohomology of these moduli spaces, but homological stability results often give a first order approximation to the homology. In this talk, we'll explain how to obtain second order homological computations for a class of Hurwitz moduli spaces of branched covers; these yield second order terms in enumerating the moduli over finite fields. We may interpret these as second order terms in a function field analogue of the function which counts number fields, ordered by discriminant. Our second order terms match those of TaniguchiThorne/BhargavaShankarTsimerman in the cubic case, and give new predictions in other Galois settings. This is joint (and ongoing) work with Berglund, Michel, and Tran. 
Mon Oct 14 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Oct 11 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Oct 11 
Combinatorics Seminar3:30pm  Vincent Hall 570KazhdanLusztig Immanants for kPositive Matrices Sunita Chepuri Abstract:Immanants are matrix functionals that generalize the determinant. One notable family of immanants are the KazhdanLusztig immanants. These immanants are indexed by permutations and are defined as sums involving KazhdanLusztig polynomials. One notable property of KazhdanLustzig immanants is that they are nonnegative on totally positive matrices. We give a condition on permutations that allows us to extend this theorem to the setting of kpositive matrices. We also conjecture a larger class of permutations for which our theorem holds true. 
Fri Oct 11 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar 
Fri Oct 11 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Oct 11 
Special Events and Seminars1:25pm  Vincent Hall 213Trace Formula (continued) Steven Sperber, University of Minnesota 
Fri Oct 11 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Data Science in Healthcare Yinglong Guo, UnitedHealth Group Abstract:UnitedHealth Group Research and Development (UHG R&D) is working on creating, validating, testing, and refining innovations in the healthcare industry. Our data science team provides technical solutions by applying various statistical and machine learning methods to a vast amount of data in order to answer research questions. In this talk, I will give a brief introduction to my daytoday experience as a data scientist. I will also discuss the methodology involved in several analyses of treatment outcomes for prostate cancer. 
Thu Oct 10 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Oct 10 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Oct 10 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar Mike Loper, University of Minnesota 
Thu Oct 10 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Oct 09 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Oct 09 
PDE Seminar3:35pm  Vincent Hall 570Diffusion in the Mean for a Periodic Schrödinger Equation Perturbed by a Fluctuating Potential Shiwen Zhang, UMN Abstract:We consider the solution to a tightbinding, periodic Schrödinger equation with a random potential evolving stochastically in time. If the potential evolves according to a stationary Markov process we obtain a positive, finite diffusion constant for the evolution of the solution. More generally, we show that the square amplitude of the wave packet, after diffusive rescaling, converges to a solution of the heat equation. (Joint work with J. Schenker and Z. Tilocco at the Michigan State University). 
Wed Oct 09 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Oct 08 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Oct 08 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Oct 08 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Oct 08 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Oct 08 
IMA Data Science Lab Seminar1:25pm  Lind 305LectureParallel Transport Convolutional Neural Networks on Manifolds Rongjie Lai, Rensselaer Polytechnic Institute Abstract:Convolution has played a prominent role in various applications in science and engineering for many years. It is also the most important operation in convolutional neural networks (CNNs). There has been a recent growth of interests of research in generalizing CNNs on 3D objects, often represented as compact manifolds. However, existing approaches cannot preserve all the desirable properties of Euclidean convolutions, namely compactly supported filters, directionality, transferability across different manifolds. In this talk, I will discuss our recent work on a new way of defining convolution on manifolds via parallel transport. This geometric way of defining parallel transport convolution (PTC) provides a natural combination of modeling and learning on manifolds. PTC allows for the construction of compactly supported filters and is also robust to manifold deformations. I will demonstrate its applications to shape analysis using deep neural networks based on parallel transportation convolutional networks (PTCnet). Dr. Rongjie Lai received his Ph.D. degree in applied mathematics from the University of California, Los Angeles, He is currently an assistant professor at the Rensselaer polytechnic Institute. Dr. Lais research interests are mainly in modern scientific computing including developing mathematical and computational tools for analyzing and processing signals, images as well as unorganized data using methods of variational partial differential equations, computational differential geometry and learning. In 2018, Dr. Lai was granted an NSF CAREER award for his research in geometry and learning for manifoldstructured data in 3D and higher dimension. 
Tue Oct 08 
Climate Seminar11:15am  Vincent Hall 570Permafrost Response to Climate Change via Budykos Model Richard McGehee, UMN 
Mon Oct 07 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Nonuniqueness in Dynamical Systems Richard McGehee, University of Minnesota Abstract:Discontinuous vector fields arise naturally in some applications. In this presentation, a simple classical model of ocean circulation is introduced as an example of how discontinuities give rise to nonunique solutions. Standard bifurcation techniques often fail when the vector field is not smooth, and certainly fail when the vector field is discontinuous. However, some topological techniques seem to carry over, and a crude birfurcation theory can be extended to a large class of discontinuous systems. 
Mon Oct 07 
Student Number Theory Seminar3:35pm  Vincent Hall 1A Tour of the padic Representation Theory of GL_2 Katy Weber Abstract:We summarize the classification of representations of GL_2 over a padic field, emphasizing the relationship between these representations and automorphic forms and Lfunctions. Time permitting, we will also discuss Whittaker models of these representations and the CasselmanShalika formula. This talk is meant to be a sketch of these results and how they fit into the bigger picture, and should be accessible even if you are not very familiar with representation theory. 
Mon Oct 07 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Oct 07 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Oct 07 
Topology Seminar2:30pm  Ford Hall 110Topology Seminar 
Mon Oct 07 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Oct 04 
MCFAM Seminar5:30pm  Vincent Hall 16RANDOM RULES AND THE ANCIENT HISTORY OF SIMULATION Arkady Shemyakin, University of St. Thomas Abstract:Modern approaches to simulation, involving Monte Carlo methods and randomized procedures of decisionmaking, are usually dated back to the mid20th century and the arrival of the computer era. Deeper history goes back to the 19th and even 18th centuries and involves such devices as Galtons board and Buffons needle. However, one can argue that long before the invention of computers, older devices such as dice and their predecessors have been effectively used for games and divination. The idea of this paper is to review the use of ancient randomizing devices to trace the history of simulation and random rules of decisionmaking. Special attention will be paid to some contemporary cultures, which have preserved some unique elements of their ancient history: native cultures of the Americas, the Celtic civilizations of Ireland and Scotland, and the indigenous peoples of Northern and Central Asia (Altai and Siberia).Bio: https://www.stthomas.edu/mathematics/faculty/arkadyshemyakin.html 
Fri Oct 04 
Probability Seminar3:30pm  Vincent Hall 311Invertibility of inhomogenuous heavytailed matrices Galyna Livshyts, Georgia Tech Abstract:We will show the sharp estimate on the behavior of the smallest singular value of random matrices under very general assumptions. One of the key steps in the proof is a result about the efficient discretization of the unit sphere in an ndimensional euclidean space. This result allows us to work with very general random matrices. The proof of the result will be outlined. Partially based on the joint work with Tikhomirov and Vershynin. 
Fri Oct 04 
Combinatorics Seminar3:30pm  Vincent Hall 570Higher cluster categories and QFT dualities Gregg Musiker Abstract:We present a unified mathematical framework that elegantly describes minimally supersymmetric gauge theories in various dimensions, and their dualities. Though this approach utilizes higher Ginzburg algebras and higher cluster categories (also known as mcluster categories), we show that the constructions can be given explicitly and combinatorially. We emphasize the connections to cluster algebras and two classes of examples: one class related to toric geometry and giving rise to brane bricks, which are 3dimensional analogues of certain bipartite graphs on surfaces, and one class corresponding to higher partial triangulations of surfaces. This is based on joint work with Sebastian Franco of City College of New York. No prior knowledge of Quantum Field Theories or Cluster Algebras will be assumed. 
Fri Oct 04 
Probability Seminar2:30pm  Vincent Hall 311Reconstruction problems on amenable graphs Ahmed El Alaoui, Stanford University Abstract:We consider the problem of reconstructing a hidden assignment of random variables (x_1, , x_n) sitting on the nodes of a graph, given noisy observations of pairs (x_u, x_v) for every edge (u,v) of the graph. Such problems have been extensively studied when the underlying graph is meanfield (e.g., the complete graph, ErdosRenyi, random regular, ), in which case the existence of a ``possiblebuthard phase where reconstruction is possible but computationally difficult is ubiquitous. In contrast, the picture is dramatically different when the graph is amenable. I will represent a generic result about the optimality of local algorithms for computing marginals under a somewhat strong model of side information. Next, I will focus on Z_2 synchronization (aka planted Ising model) on the Euclidean lattice with weaker side information, and discuss a renormalizationbased procedure for reconstructing the assignment. Joint work with Andrea Montanari. 
Fri Oct 04 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Oct 04 
Special Events and Seminars1:25pm  Vincent Hall 213"Trace Formula, I" Steven Sperber, University of Minnesota 
Thu Oct 03 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Oct 03 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Oct 03 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Linkage, and the licci conjecture on grade 3 perfect ideals Mahrud Sayrafi, University of Minnesota Abstract:Let Q be a regular local ring. An ideal I in Q is said to be licci if it is in the linkage class of a complete intersection. Christensen, Veliche and Weyman conjectured that a perfect ideal of grade 3 in Q is licci if and only if its free resolution corresponds to Dynkin diagrams. After introducing the theory of linkage, I will talk about the conjecture, how Dynkin diagrams are involved, and their approach in showing one direction of the conjecture in arXiv:1712.04016. 
Thu Oct 03 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Thu Oct 03 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Language and Interaction in Minecraft Arthur Szlam, Facebook Abstract:I will discuss a research program aimed at building a Minecraft assistant, in order to facilitate the study of agents that can complete tasks specified by dialogue, and eventually, to learn from dialogue interactions. I will describe the tools and platform we have built allowing players to interact with the agents and to record those interactions, and the data we have collected. In addition, I will describe an initial agent from which we (and hopefully others) can iterate. 
Wed Oct 02 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Oct 02 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Wed Oct 02 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Oct 01 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Oct 01 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Oct 01 
Dynamical Systems2:30pm  Vincent Hall 209Relative equilibrium configurations of gravitationally interacting rigid bodies Rick Moeckel, University of Minnesota Abstract:Consider a collection of n rigid, massive bodies interacting according to their mutual gravitational attraction. A relative equilibrium motion is one where the entire configuration rotates rigidly and uniformly about a fixed axis all of the bodies are phase locked. Such a motion is possible only for special positions and orientations of the bodies. A minimal energy motion is one which has the minimum possible energy in its fixed angular momentum level. While every minimal energy motion is a relative equilibrium motion, the main result here is that a relative equilibrium motion of n >= 3 disjoint rigid bodies is never an energy minimizer. Since energy minimizers are the expected final states produced by tidal interactions, phase locking of 3 or more bodies will not occur. 
Tue Oct 01 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Oct 01 
IMA Data Science Lab Seminar1:25pm  Lind 305Citizen Science and Machine Learning at Zooniverse Darryl Wright, University of Minnesota, Twin Cities Abstract:As researchers gather everlarger datasets there is an increasing demand for citizen science and reliance on machine learning. We will introduce Zooniverse, the world's largest citizen science platform, and show how citizen scientists are helping researchers extract meaningful information from their data. But the demand for citizen scientists and the volumes of data they are being asked to process is beginning to tax even the abilities of our 1.8 million volunteers. We will show how machine learning is being deployed to ease some of this burden and show how machine learning and citizen science can empower each other to process data more efficiently than either alone. 
Tue Oct 01 
Climate Seminar11:15am  Vincent Hall 570"An Introduction to Budyko's Energy Balance Model" Richard McGehee 
Mon Sep 30 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Sep 30 
Student Number Theory Seminar3:35pm  Vincent Hall 1Leading up to Dirichlets class number formula Dev Hegde Abstract:The talk will give a historical introduction to number theory leading up to Dirichlets class number formula which was one of the biggest achievements of analytic methods in number theory. No background is necessary to understand the talk. 
Mon Sep 30 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Sep 30 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 30 
Topology Seminar2:30pm  Ford Hall 110Mysterious Duality Sasha Voronov, University of Minnesota Abstract:Mysterious Duality was discovered by Iqbal, Neitzke, and Vafa in 2001. They noticed that toroidal compactifications of Mtheory lead to the same series of combinatorial objects as del Pezzo surfaces do, along with numerous mysterious coincidences: both toroidal compactifications and del Pezzo surfaces give rise to the exceptional series E_k; the Uduality group corresponds to the Weyl group W(E_k), arising also as a group of automorphisms of the del Pezzo surface; a collection of various M and Dbranes corresponds to a set of divisors; the brane tension is related to the area of the corresponding divisor, etc. The mystery is that it is not at all clear where this duality comes from. In the talk, I will present another series of mathematical objects: certain versions of multiple loop spaces of the sphere S^4, which are, on the one hand, directly connected to Mtheory and its combinatorics, and, on the hand, possess the same combinatorics as the del Pezzo surfaces. This is a report on an ongoing work with Hisham Sati. 
Mon Sep 30 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Sep 27 
MCFAM Seminar5:30pm  Vincent Hall 16Positive Matrices and Derivative Models Carlos Tolmasky, University of Minnesota Abstract:Principal components analysis has become widely used in a variety of fields. In finance and, more specifically, in the theory of interest rate derivative modeling, its use has been pioneered by R. Litterman and J. Scheinkman. Their key finding was that a few components explain most of the variance of treasury zerocoupon rates and that the first three eigenvectors represent level, slope and curvature changes on the curve. This result has been, since then, observed in various markets.Over the years, there have been several attempts at modeling correlation matrices displaying the observed effects as well as trying to understand what properties of the those matrices are responsible for the effect. Using recent results of the theory of positive matrices we characterize these matrices and, as an application, we shed light on some of the critiques to this methodology.Bio: http://mcfam.math.umn.edu/people/carlostolmasky 
Fri Sep 27 
Combinatorics Seminar3:30pm  Vincent Hall 570A positivity phenomenon in Elser's Gaussiancluster percolation model Galen DorpalenBarry, University of Minnesota Abstract:Veit Elser proposed a random graph model for percolation in which physical dimension appears as a parameter. Studying this model combinatorially leads naturally to the consideration of numerical graph invariants which we call \textit{Elser numbers} \text{els}_k(G), where G is a connected graph and k a nonnegative integer. Elser had proven that \text{els}_1(G)=0 for all G. By interpreting the Elser numbers as Euler characteristics of appropriate simplicial complexes called \emph{nucleus complexes}, we prove that for all graphs G, they are nonpositive when k=0 and nonnegative for k\geq2. The last result confirms a conjecture of Elser. At the end, we will present an open problem naturally arising from our proof of Elser's conjecture. 
Fri Sep 27 
Probability Seminar2:30pm  Vincent Hall 311Random matrices, operators and analytic functions Benedek Valko, UW Madison Abstract:The finite circular betaensembles and their point process scaling limit can be represented as the spectra of certain random differential operators. These operators can be realized on a single probability space so that the point process scaling limit is a consequence of an operator level limit. The construction allows the derivation of the scaling limit of the normalized characteristic polynomials of the finite models to a random analytic function. I will review these representations and constructions, and present a couple of applications. Joint with B. Virág (Toronto). 
Fri Sep 27 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Sep 27 
Special Events and Seminars1:25pm  Vincent Hall 213A padic analytic interpolation of a finite field character, II Steven Sperber, University of Minnesota 
Fri Sep 27 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Sampling from an Alternate Universe: Overview of Privacypreserving Synthetic Data Christine Task, Knexus Research Corporation Abstract:Data accessibility is importantpublicly available datasets support vital social science research, social programs and datainformed governance. In recent years, an increasing amount of data has been curated and made generally available through sites like data.gov, IPUMS, and other resources, fueling the progress of research in Big Data. However, data with the most potential value for public good can also be the most privacy sensitivesuch as data on abuse, STDS, extreme poverty, or mental health. These datasets exist, but may be redacted or entirely withheld from public view due to legal restrictions and the very real danger that anonymized individuals may be reidentified. Privacypreserving synthetic data provides a pathway to publicly release datasets that contain very sensitive information. The basic process consists of three parts: A generative model is built which captures the distribution of the original sensitive data, perturbation steps are applied to the model to improve its privacy properties (either formal or heuristicbased), and then the model is used to synthesize a new data set of synthetic individuals. The synthetic dataset preserves the significant properties of the original data, but because it contains no real people, it can be safely released to the public. When the distributional difference between the real and synthetic data mimics the difference between two subsamples of the original data, i.e. when privacy error mimics sampling error, we can think of the synthetic data as survey results from a parallel dimension: The same pattern of information as the original data, with no real people. In this talk, I'll cover approaches to creating synthetic data, the difference between formal and heuristicbased privacy, and, importantly, quality metrics used to verify that the synthetic data is a good substitute for the original data (a challenging problem itself in a high dimensional feature space). High quality synthetic data is a rapidly progressing research area, with both promising success stories and an exciting frontier of open problems. 
Thu Sep 26 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Sep 26 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Sep 26 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Global Sections of Toric Vector Bundles Jorin Schug Abstract:This talk will continue to follow the "Parliament of Polytopes" paper by Di Rocco, Jabbusch, and Smith. I'll discuss the result that the Tequivariant generators for the global sections of a toric vector bundle E correspond to the lattice points in the parliament of polytopes for E and look to understand this result for some examples, including direct sums of line bundles. 
Thu Sep 26 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Wed Sep 25 
PDE Seminar3:35pm  Vincent Hall 570Random Tug of War games for the pLaplacian Marta Lewicka, University of Pittsburgh Abstract:We propose a new dynamic programming principle related to the Dirichlet problem for the homogeneous pLaplace equation in connection with the Tug of War games with noise. We also discuss similar approximations in presence of the Robin boundary conditions. For the proofs, we use martingale techniques involving various couplings of random walks and yielding estimates on the involved probabilistic representations. 
Wed Sep 25 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Sep 25 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Sep 24 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Sep 24 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Sep 24 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Sep 24 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology TBA 
Tue Sep 24 
IMA Data Science Lab Seminar1:25pm  Lind 305The Geometry of Ambiguity in Onedimensional Phase Retrieval Dan Edidin, University of Missouri Abstract:The phase retrieval problem is the problem of reconstructing an unknown signal from its Fourier intensity function. This problem has a long history in physics and engineering and occurs in contexts such as Xray crystallography, speech processing and computational biology. As stated, the phase retrieval problem is illposed as there may be up to $2^N$ nonequivalent signals (called ambiguities) with the same Fourier intensity function. To enforce uniqueness additional constraints must be imposed. In this talk we discuss the geometry of the space of ambiguities obtained by varying the signal. By understanding this geometry we prove a general result characterizing constraints that enforce a unique solution to the phase retrieval problem. This result was applied in work with Tamir Bendory and Yonina Eldar on blind phaseless shorttime Fourier transform recovery. 
Tue Sep 24 
Climate Seminar11:15am  Vincent Hall 570An Introduction to Planetary Energy Balance Richard McGehee, University of Minnesota 
Mon Sep 23 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Sep 23 
Student Number Theory Seminar3:35pm  Vincent Hall 1Elliptic Curves Claire Frechette 
Mon Sep 23 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
Mon Sep 23 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 23 
Topology Seminar2:30pm  Ford Hall 110Homology class of DeligneLusztig varieties Dongkwan Kim, University of Minnesota Abstract:Since first defined by Deligne and Lusztig, a DeligneLusztig variety has become unavoidable when studying the representation theory of finite groups of Lie type. This is a certain subvariety of the flag variety of the corresponding reductive group, and its cohomology groups are naturally endowed with the action such finite groups, which in turn gives a decomposition of irreducible representations called Lusztig series. In this talk, I will briefly discuss the background of DeligneLusztig theory and provide a formula to calculate the homology class of DeligneLusztig varieties in the Chow group of the flag variety. If time permits, I will also discuss their analogues. 
Mon Sep 23 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Sep 20 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Student Research  Outcome analysis of Indexed Universal Life Insurance based on Monte Carlo Simulation Songyu Yan and Ian Luo, University of Minnesota Abstract:Indexed Universal Life (IUL) Insurance was developed to harness thepower of equity market returns with downside protection. However IUL iscurrently illustrated using a static credited rate which masks market returnvolatility inherent in its structure. As a result, what policyholders see as expectedperformance maybe far from reality in many cases. In our research, we modeledthe pricing algorithms of major IUL products and applied scenario testing usingMonte Carlo simulation of indices used in IUL products. The statistical variance ofindices leads to vastly different results than what is currently demonstrated inmany cases, and this variance may cause the failure of the policy. Our researchindicates a better method for demonstrating policy performance would be basedon an outcome analysis rather than the static method currently in use.Bios: Songyu Yan: https://www.linkedin.com/in/songyuyan826bb2126/ Ian Luo: https://www.linkedin.com/in/yifeiluo9051b1170/ 
Fri Sep 20 
Combinatorics Seminar3:30pm  Vincent Hall 570Cyclic Sieving for planet partitions and symmetry Sam Hopkins., University of Minnesota Abstract:The cyclic sieving phenomenon of Reiner, Stanton, and White says that we can often count fixed points for a cyclic group acting on a combinatorial set by plugging roots of unity into a polynomial related to this set. One of the most impressive instances of the cyclic sieving phenomenon is a theorem of Rhoades asserting that the set of plane partitions in a rectangular box under the action of promotion exhibits cyclic sieving. In Rhoades's result the sieving polynomial is the size generating function for these plane partitions, which has a wellknown product formula due to MacMahon. We extend Rhoades's result by studying the interaction of promotion with symmetries of plane partitions. We obtain cyclic sievinglike formulas in this context where the relevant polynomial is the size generating function for symmetric plane partitions, whose product formula was conjectured by MacMahon and proved by Andrews. We then go on to consider the way the symmetries interact with rowmotion, another operator acting on plane partitions which is closely related to promotion. We end by explaining the connection of our work to some earlier conjectures we made concerning rowmotion acting on the Ppartitions of various triangular posets P. 
Fri Sep 20 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar 
Fri Sep 20 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Sep 20 
Special Events and Seminars1:25pm  Vincent Hall 213A padic analytic interpolation of a finite field character Steven Sperber, University of Minnesota 
Fri Sep 20 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 409SIAM Industrial Panel ,  
Thu Sep 19 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Sep 19 
Colloquium3:35pm  Vincent Hall 16The Langlands Program: An Introduction and Recent Progress Solomon Friedberg,, Boston College Abstract:The Langlands Program, connecting algebra, analysis and geometry in diverse ways, is foundational to modern number theory. I will introduce this program and indicate some recent progress. As we shall see, a great deal still remains to be done. 
Thu Sep 19 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Sep 19 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar 
Thu Sep 19 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570D=4, N=1 Compactifications of Maximal Supergravities via Generalised Geometry  Kahler potentials, superpotentials and moduli David Tennnyson, Imperial College London Abstract:We analyse compactifications of 11 dimensional or type II supergravity down to 4 dimensional Minkowski space for generic flux and generic internal Killing spinors. We note the failure of conventional differential geometry to capture the generic features of the theory and show that the correct formalism comes in the form of a closed form Leibniz algebroid  or as we call it in the physics community, generalised geometry. Our structure is similar to the generalised geometry of Hitchin, but now the structure group is the noncompact exceptional group E_{7(7)}x R^{+}. It turns out that having N=1 supersymmetry in the effective theory on Minkowski space is equivalent to an integrable SU(7) structure on the generalised tangent bundle. We provide the tensors that define the SU(7) structure and give the integrability conditions. Finally we provide an expression for the Kahler potential on the space of structures, the superpotential of the lower dimensional theory, and we explore the moduli of these structures giving explicit answers in certain cases. 
Wed Sep 18 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Sep 18 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Wed Sep 18 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Siegel's extensions of Epstein zeta functions as Eisenstein series Paul Garrett, University of Minnesota 
Tue Sep 17 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Sep 17 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue Sep 17 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Sep 17 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology 
Tue Sep 17 
IMA Data Science Lab Seminar1:25pm  Lind 305Optimal Recovery under Approximability Models, with Applications Simon Foucart, Texas A & M University Abstract:For functions acquired through point evaluations, is there an optimal way to estimate a quantity of interest or even to approximate the functions in full? We give an affirmative answer to this question under the novel assumption that the functions belong to a model set defined by approximation capabilities. In fact, we produce implementable linear algorithms that are optimal in the worstcase setting. We present applications of the abstract theory in atmospheric science and in system identification. Dr. Simon Foucart earned a Masters of Engineering from the Ecole Centrale Paris and a Masters of Mathematics from the University of Cambridge in 2001. In 2006, he received his Ph.D. in Mathematics at the University of Cambridge, specializing in Approximation Theory. After two postdoctoral positions at Vanderbilt University and Université Paris 6, he joined Drexel University in 2010 before moving to the University of Georgia in 2013. Since 2015, he has been with Texas A&M University, where is now professor. His recent work focuses on the field of Compressive Sensing, whose theory is exposed in the book A Mathematical Introduction to Compressive Sensing he coauthored with Holger Rauhut. Dr. Foucarts research was recognized by the Journal of Complexity, from which he received the 2010 Best Paper Award. Dr. Foucarts current interests also include the mathematical aspects of Metagenomics, Optimization, Deep Learning and Data Science at Large 
Tue Sep 17 
Climate Seminar11:15am  Vincent Hall 570The Scientific Case for Anthropogenic Warming II Richard McGehee, University of Minnesota 
Mon Sep 16 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Sep 16 
Student Number Theory Seminar3:35pm  Vincent Hall 1A Brief Introduction to LFunctions Joe Dickinson Abstract:Like Andy's talk last week, this week will be another introductory talk; the topic is Lfunctions. We will start with a discussion of Dirichlet's use of Lseries to show the infinitude of primes in arithmetic progressions, then proceed to how Lfunctions have become a major area of investigation. We will discuss only a sampling of topics, with the goal of motivating interest and setting the stage for future talks. 
Mon Sep 16 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 16 
Topology Seminar2:30pm  Ford Hall 110Transfer in the homology and cohomology of categories Peter Webb, University of Minnesota Abstract:The cohomology of a category has many properties that extend those that are familiar when the category is a group. Second cohomology classifies equivalence classes of category extensions, first cohomology parametrizes conjugacy classes of splittings, first homology is the abelianization of the fundamental group, and second homology has a theory that extends that of the Schur multiplier. Defining restriction and corestriction maps on the homology of categories is problematic: most attempts to do this require induction and restriction functors to be adjoint on both sides, and this typically does not happen with categories. We describe an approach to defining these maps that includes all the situations where they can be defined in group cohomology, at least when the coefficient ring is a field. The approach uses bisets for categories, the construction by Bouc and Keller of a map on Hochschild homology associated to a bimodule, and the realization by Xu of category cohomology as a summand of Hochschild cohomology. 
Mon Sep 16 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Sep 13 
MCFAM Seminar5:30pm  Vincent Hall 16MFM Alumni/Student Panel: How the MFM Prepares You to Enter the Field of Quantitative Finance MFM Alumni/Student Panel, Master of Financial Mathematics Program (MFM) Abstract:Learn from current students and MFM alumni in industry about the benefits of this professional master program. Panelists will talk about what attracted them to the program, how to make the most of your time in the MFM and why the practical, realworld learning helps you land jobs in quantitative risk analysis, hedging, trading, portfolio management, fintech, data analytics and other jobs that are hot in the field right now. 
Fri Sep 13 
Combinatorics Seminar3:30pm  Vincent Hall 570Combinatorics Seminar 
Fri Sep 13 
Probability Seminar2:30pm  Vincent Hall 311Critical behavior for percolation on graphs with given degrees Souvik Dhara, MIT Abstract:We discuss critical behavior of percolation on finite random networks. In a seminal paper, Aldous (1997) identified the scaling limit for the component sizes in the critical window of phase transition for the ErdosRenyi random graph (ERRG). Subsequently, there has been a surge in the literature, revealing several interesting scaling limits of these critical components, namely, the component size, diameter, or the component itself when viewed as a metric space. Fascinatingly, when the third moment of the asymptotic degree distribution is finite, many random graph models have been shown to exhibit a universality phenomenon in the sense that their scaling exponents and limit laws are the same as the ERRG. In contrast, when the asymptotic degree distribution is heavytailed (having an infinite third moment), the limit law turns out to be fundamentally different from the ERRG case and in particular, becomes sensitive to the precise asymptotics of the highest degree vertices. In this talk, we will focus on random graphs with a prescribed degree sequence. We start by discussing recent scaling limit results, and explore the universality classes that arise from heavytailed networks. Of particular interest is a new universality class that arises when the asymptotic degree distribution has an infinite second moment. Not only it gives rise to a completely new universality class, it also exhibits several surprising features that have never been observed in any other universality class so far. This is based on joint works with Shankar Bhamidi, Remco van der Hofstad, Johan van Leeuwaarden and Sanchayan Sen. 
Fri Sep 13 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Sep 13 
Special Events and Seminars1:25pm  Vincent Hall 213"pAdic Cohomology, Exponential Sums, and Hypergeometric Functions TBA 
Fri Sep 13 
Probability Seminar9:30am CANCELLED 
Thu Sep 12 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Sep 12 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Sep 12 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar 
Thu Sep 12 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology 
Wed Sep 11 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Sep 11 
PDE Seminar3:35pm  Vincent Hall 570Parabolic problems with rough coefficients Pierre Portal,, Australian National University Abstract:Using form methods, one can solve linear parabolic PDE in divergence form with $L^2$ data in appropriate energy spaces, even when the coefficients are merely bounded measurable in time and space, and no maximum principle is available. This goes back, at least, to the work of Lions and his school in the 1950s. When dealing with $L^p$ data, it is not so clear which $L^p$ like solution space one should use as a replacement of Lions energy space. Depending on the choice, one can solve, for instance, time dependent single equations (Aronson 1968), time independent systems for a range of values of $p$ (Auscher 2005), or stochastic problems with some spatial regularity (starting with Krylov 1994). This summarises joint works with Pascal Auscher, Sylvie Monniaux, Jan van Neerven, and Mark Veraar. 
Wed Sep 11 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Tue Sep 10 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Sep 10 
Colloquium3:30pm  VinH 16Colloquium 
Tue Sep 10 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Sep 10 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology 
Tue Sep 10 
IMA Data Science Lab Seminar1:25pm  Lind 305Taming Nonconvexity: From Smooth to Nonsmooth Problems and Beyond Ju Sun, University of Minnesota, Twin Cities Abstract:Most applied problems we encounter can be naturally written as nonconvex optimization, for which In this talk, I will describe our recent effort in bridging the mysterious theorypractice gap for nonconvex optimization, in the context of solving practical problems in signal processing, machine learning, and scientific imaging. 1) I will highlight a family of smooth nonconvex problems that can be solved to global optimality using simple numerical methods, independent of initialization. 2) The discovery, however, does not cover nonsmooth functions, which are frequently used to encode structural objects (e.g., sparsity) or achieve robustness. I will introduce tools from nonsmooth analysis, and demonstrate how nonsmooth, nonconvex problems can also be analyzed and solved in a provable manner. 3) Toward the end, I will provide examples to show how innovative problem formulation and physical design can help to tame nonconvexity. Ju Sun is an assistant professor at the computer science & engineering department, University of Minnesota at Twin Cities. Prior to this, he was a postdoctoral scholar at Stanford University, 
Tue Sep 10 
Climate Seminar11:15am  Vincent Hall 570"The Scientific Case for Anthropogenic Warming" Richard McGehee, University of Minnesota 
Mon Sep 09 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Emergent behavior in collective dynamics Eitan Tadmor, University of Maryland Abstract:Collective dynamics is driven by alignment that tend to selforganize the crowd and by different external forces that keep the crowd together. Different emerging equilibria are selforganized into clusters, flocks, tissues, parties, etc. I will overview recent results on the hydrodynamics of largetime, largecrowd collective behavior, driven by different rules of engagement. In particular, I address the question how shortrange interactions lead, over time, to the emergence of longrange patterns, comparing geometric vs. topological interactions. 
Mon Sep 09 
Student Number Theory Seminar3:35pm  Vincent Hall 1Student Number Theory Seminar 
Mon Sep 09 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 09 
Topology Seminar2:30pm  Ford Hall 110Cohomology of the space of complex irreducible polynomials in several variables Weiyan Chen, University of Minnesota Abstract:We will show that the space of complex irreducible polynomials of degree d in n variables satisfies two forms of homological stability: first, its cohomology stabilizes as d increases, and second, its compactly supported cohomology stabilizes as n increases. Our topological results are inspired by counting results over finite fields due to Carlitz and Hyde. 
Mon Sep 09 
Cockburn's Seminar2:30pm  Ford Hall B15Cockburn's Seminar 
Fri Sep 06 
Combinatorics Seminar3:30pm  Vincent Hall 570Combinatorics Seminar 
Fri Sep 06 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar 
Fri Sep 06 
Reading Seminar on Automorphic Forms1:30pm  Vincent Hall 1Reading Seminar on Automorphic Forms 
Fri Sep 06 
Probability Seminar9:30am CANCELLED 
Thu Sep 05 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra seminar 
Thu Sep 05 
Colloquium3:35pm  Vincent Hall 16Colloquium  Canceled Alina Chertock, NSCU Abstract:Chemotaxis is a movement of microorganisms or cells towards the areas of high concentration of a certain chemical, which attracts the cells and may be either produced or consumed by them. In its simplest form, the chemotaxis model is described by a system of nonlinear PDEs: a convectiondiffusion equation for the cell density coupled with a reaction diffusion equation for the chemoattractant concentration. It is wellknown that solutions of such systems may develop spiky structures or even blow up in finite time provided the total number of cells exceeds a certain threshold. This makes development of numerical methods for chemotaxis systems extremely delicate and challenging task. In this talk, I will present a family of highorder numerical methods for the KellerSegel chemotaxis system and several related models. Applications of the proposed methods to to multiscale and coupled chemotaxisfluid system and will also be discussed. 
Thu Sep 05 
Commutative Algebra Seminar2:30pm  Vincent Hall 209Commutative Algebra Seminar 
Thu Sep 05 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology 
Wed Sep 04 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
Wed Sep 04 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Tue Sep 03 
Special Events and Seminars4:30pm  Vincent Hall 301Arithmetic Geometry Seminar 
Tue Sep 03 
Colloquium3:30pm  VinH 16Colloquium 
Tue Sep 03 
Dynamical Systems2:30pm  Vincent Hall 209Dynamical Systems Seminar 
Tue Sep 03 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry and Sympletic Topology 
Tue Sep 03 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Sep 02 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Aug 30 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Aug 30 
Probability Seminar9:30am CANCELLED 
Thu Aug 29 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Tue Aug 27 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar TBA 
Mon Aug 26 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Aug 23 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Aug 23 
Probability Seminar9:30am CANCELLED 
Mon Aug 19 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Aug 16 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Aug 16 
Probability Seminar9:30am CANCELLED 
Wed Aug 14 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Mon Aug 12 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Aug 12 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Fri Aug 09 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Aug 09 
Probability Seminar9:30am CANCELLED 
Wed Aug 07 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Mon Aug 05 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Aug 05 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Fri Aug 02 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Aug 02 
Probability Seminar9:30am CANCELLED 
Wed Jul 31 
Combinatorics Seminar3:35pm  Vincent Hall 16Hurwitz action of reflection factorizations of Coxeter elements Sophiane Yahiatene, Bielefeld University Abstract:In the talk we will investigate a natural braid group action on factorizations of elements in reflection groups. In particular, we will consider reflection factorizations of Coxeter elements in Coxeter groups of finite rank and state conditions whether two factorizations lie in the same orbit under the natural action. The presented result extends the investigation of Lewis  Reiner (arXiv:1603.05969) to arbitrary Coxeter groups of finite rank. (j.w. Patrick Wegener) 
Wed Jul 31 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Mon Jul 29 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jul 29 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Fri Jul 26 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Jul 26 
Probability Seminar9:30am CANCELLED 
Wed Jul 24 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Tue Jul 23 
Combinatorics Seminar3:35pm  Vincent Hall 113Enumeration of bounded lecture hall tableaux Jang Soo Kim,, Sungkyunkwan University Abstract:Recently Corteel and Kim introduced lecture hall tableaux in their study of multivariate little qJacobi polynomials. In this talk, we enumerate bounded lecture hall tableaux. We show that their enumeration is closely related to standard and semistandard Young tableaux. We also show that the number of bounded lecture hall tableaux is the coefficient of the Schur expansion of s?(m+y1,...,m+yn). To prove this result, we use two main tools: nonintersecting lattice paths and bijections. In particular we use ideas developed by Krattenthaler to prove bijectively the hook content formula. This is joint work with Sylvie Corteel. 
Mon Jul 22 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jul 22 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Fri Jul 19 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Jul 19 
Probability Seminar9:30am CANCELLED 
Thu Jul 18 
Combinatorics Seminar3:35pm  Vincent Hall 16Fibers of maps to totally nonnegative spaces and the FominShapiro Conjecture Patricia Hersh, North Carolina State University Abstract:Anders Björner and Joseph Bernstein raised the question of finding regular CW complexes naturally arising from representation theory having the intervals of Bruhat order as their posets of closure relations. Sergey Fomin and Michael Shapiro conjectured a solution, namely the link of the identity in the totally nonnegative real part of the unipotent radical of a Borel in a semisimple, simply connected algebraic group defined and split over the reals together with a family of related spaces indexed by the different Coxeter group elements. The FominShapiro conjecture indeed proved to be true, with the proof utilizing an interpretation of these stratified spaces as images of an intriguing family of maps  maps also arising in work of Lusztig related to canonical bases. I will start by reviewing some highlights of this story, then turn to recent joint work with Jim Davis and Ezra Miller regarding the structure of the fibers of these same maps. 
Wed Jul 17 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Mon Jul 15 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jul 15 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Fri Jul 12 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Jul 12 
Probability Seminar9:30am CANCELLED 
Wed Jul 10 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Mon Jul 08 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jul 08 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Fri Jul 05 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Jul 05 
Probability Seminar9:30am CANCELLED 
Wed Jul 03 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Mon Jul 01 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jul 01 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Fri Jun 28 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Jun 28 
Probability Seminar9:30am CANCELLED 
Wed Jun 26 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Mon Jun 24 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jun 24 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Fri Jun 21 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Jun 21 
Probability Seminar9:30am CANCELLED 
Wed Jun 19 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Mon Jun 17 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jun 17 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Fri Jun 14 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Jun 14 
Probability Seminar9:30am CANCELLED 
Wed Jun 12 
Special Events and Seminars1:30pm  Vincent Hall 364Summer Student Representation Theory Seminar 
Mon Jun 10 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jun 10 
Special Events and Seminars1:30pm  Vincent Hall 364Basic Operations on Representations Andy Hardt Abstract:We continue our crash course in finite group representation theory by looking at some important operations on representations. We start by defining the group algebra of a finite group; group representations naturally biject with modules over the group algebra. After that, we'll talk through a variety of ways to construct new representations from old, such as restriction, induction, inflation, tensor product, and we may even squeeze in symmetric and exterior powers. 
Fri Jun 07 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri Jun 07 
Probability Seminar9:30am CANCELLED 
Thu Jun 06 
Combinatorics Seminar3:35pm  Vincent Hall 113Chicken Nuggets and Numerical Semigroups Ayomikun Adeniran, Texas A&M Abstract:A numerical semigroup is a subset of N that is closed under addition, contains 0 and has finite complement in N. There are several fundamental invariants of a numerical semigroup S among which are the Frobenius number and genus of S, denoted F(S) and g(S), respectively. The quotient of a numerical semigroup S by a positive integer d is the set S/d={xdx?S} which is also a numerical semigroup. In this talk, I will present some recent results showing the relation between the genus of S/d and the genus of S. If time permits, we will also talk about identities relating the Frobenius numbers and the genus of quotients of numerical semigroups that are generated by certain types of arithmetic progressions. This is joint work with S. Butler, C. Defant, Y. Gao, P.E. Harris, C. Hettle, Q. Liang, H. Nam, and A. Volk. 
Wed Jun 05 
Special Events and Seminars2:00pm  Vincent Hall 570AWM Talk Mimi Boutin 
Tue Jun 04 
Special Events and Seminars3:35pm  Vincent Hall 113Special Events and Seminars 
Tue Jun 04 
Combinatorics Seminar3:35pm  Vincent Hall 113Counting core partitions and numerical semigroups using polytopes Hayan Nam, University of California at Irvine Abstract:A partition is an aacore partition if none of its hook lengths are divisible by aa. It is well known that the number of aacore partitions is infinite and the number of simultaneous (a,b)(a,b)core partitions is a generalized Catalan number if aa and bb are relatively prime. In the first half of the talk, we give an expression for the number of simultaneous (a1,a2, ,ak)(a1,a2, ,ak)core partitions that is equal to the number of integer points in a polytope. In the second half, we discuss objects closely related to core partitions, called numerical semigroups, which are additive monoids that have finite complements in the set of nonnegative integers. For a numerical semigroup SS, the genus of SS is the number of elements in ??SN?S and the multiplicity is the smallest nonzero element in SS. In 2008, BrasAmorós conjectured that the number of numerical semigroups with genus gg is increasing as gg increases. Later, Kaplan posed a conjecture that implies BrasAmorós conjecture. In this talk, we prove Kaplan's conjecture when the multiplicity is 4 or 6 by counting the number of integer points in a polytope. Moreover, we find a formula for the number of numerical semigroups with multiplicity 4 and genus gg. 
Mon Jun 03 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri May 31 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar TBA 
Fri May 31 
Probability Seminar9:30am CANCELLED 
Wed May 29 
Special Events and Seminars1:30pm  Vincent Hall 206Informal Fluids Seminar Raj Beekie 
Mon May 27 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri May 24 
Probability Seminar9:30am CANCELLED 
Tue May 21 
Math Physics Seminar12:20pm  Vincent Hall 209Second quantization of elliptic CalogeroSutherland models Bjorn Berntson Abstract:CalogeroSutherland models are a class of completely integrable (quantum) manybody systems. In the most general case, particles interact pairwise through an elliptic potential. We discuss the second quantization of several elliptic CalogeroSutherland models. In degenerate (trigonometric, rational) cases, there is a wellstudied correspondence between CalogeroSutherland systems and BenjaminOno equations, a nonlinear, integrable integrodifferential equation. We discuss the correspondence in the elliptic regime, where second quantization of a particular system leads to a new twocomponent elliptic BenjaminOno equation. We construct a Lax pair for this equation via a RiemannHilbert problem on the torus. This is joint work with Edwin Langmann and Jonatan Lenells. 
Mon May 20 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri May 17 
Probability Seminar9:30am CANCELLED 
Thu May 16 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu May 16 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Tue May 14 
Special Events and Seminars3:30pm  Vincent Hall 570Singularity formation for some solutions of the incompressible Euler equation Tarek Elgindi Abstract:We describe a recent construction of selfsimilar blowup solutions of the incompressible Euler equation. A consequence of the construction is that there exist finiteenergy $C^{1,a}$ solutions to the Euler equation which develop a singularity in finite time for some range of $a>0$. The approach we follow is to isolate a simple nonlinear equation which encodes the leading order dynamics of solutions to the Euler equation in some regimes and then prove that the simple equation has stable selfsimilar blowup solutions. 
Tue May 14 
Math Physics Seminar12:30pm  Vincent Hall 2093rd order symmetries for systems on the 2sphere and the 2 twosheet 2hyperboloid  Superintegrability and cubic algebras Willard Miller, University of Minnesota (Joint with Ian Marquette, University of Queensland, and Bjorn Berntson, KTH Royal Institute of Techn Abstract:There are many papers concerning 3rd and higher order superintegrable systems on 2D Euclidean space, particularly by Pavel Winternitz, his students and collaborators. However, we are not aware of similar studies on nonflat spaces. We decided to study the 2sphere (with separation in polar coordinates) and the 2hyperboloid (with separation in horospherical coordinates). The computations were very complex for these nonflat systems and the results less rich than for flat space, which is to be expected. In each case we have a Hamiltonian operator H a 2nd order symmetry operator A and compute a 3rd order symmetry operator B. a nonzero B. They fall into 4 classes: 1) Systems that are 2nd order superintegrable, 2) Systems that are 3rd order superintegrable but do not generate a cubic algebra, 3) Systems with algebraically dependent generators A and B, 4) Systems that are 3rd order superintegrable with a cubic algebra. We pay special attention to the class 3 cases which also occur for Euclidian space with little change. We call these functionally dependent superintegrable systems, and show that they always permit a computation of the A eigenfunctions by simple quadrature. For the hyperboloid we show that the TTW method applied to a 2nd order 
Tue May 14 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Mon May 13 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri May 10 
First Year Seminar5:30pm  Vincent 364First Year Seminar TBA 
Fri May 10 
Combinatorics Seminar3:35pm  Vincent Hall 570Facial weak order in hyperplane arrangements Aram Dermenjian, UQAM Abstract:We discuss the facial weak order, a poset structure that extends the poset of regions on a central hyperplane arrangement to the set of all faces of the arrangement which was first introduced on the braid arrangements by Krob, Latapy, Novelli, Phan and Schwer. We provide various characterizations of this poset including a global one, a local one, one using covectors and a geometric one using the associated zonotope. We then show that the facial weak order is in fact a lattice for simplicial hyperplane arrangements, generalizing a result by Björner, Edelman and Zieglar showing the poset of regions is a lattice for simplicial arrangements. We end by stating some properties on the facial weak order. 
Fri May 10 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri May 10 
Probability Seminar9:30am CANCELLED 
Thu May 09 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu May 09 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu May 09 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu May 09 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Thu May 09 
Student Number Theory Seminar11:00am  Vincent Hall 213Student Number Theory Seminar 
Wed May 08 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Wed May 08 
AMS Intro to Research Seminar5:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed May 08 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Algebraic Representation Theory 
Wed May 08 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Tue May 07 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue May 07 
Math Physics Seminar12:20pm  Vincent Hall 209Polytopes and elliptopes in the foundations of quantum mechanics Michael Janas and Michel Janssen, School of Physics and Astronomy, University of Minnesota Abstract:Bell's inequality for classical correlations is perhaps the most famous result in quantum foundations. Less familiar is the socalled Tsirelson bound, for the corresponding quantum correlations. We first review Bell's inequality in its original form, where one attempts to classically simulate the following quantum experiment: Alice and Bob independently measure a spin component of one of a pair of spin1/2 particles entangled in the singlet state. We show that the resulting set of classical and quantum correlations allowed in this setup may be visualized as a tetrahedron and an elliptope, respectively, in threedimensional space. We then consider how to generalize these results to the case of either more settings or more outcomes (i.e., higher spin). In the case of more than two outcomes, the restrictions on the classical simulations lead to highdimensional polytopes and highlyfaceted polyhedra. In the case of four settings we arrive at the ClauserHorneShimonyHolt (CHSH) inequality, a form of the Bell inequality commonly used in experimental tests. In this context, we briefly discuss connections to semidefinite programming and the topic of spectrahedral shadows. 
Tue May 07 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Mon May 06 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Mon May 06 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Classical Properties of Epstein zeta functions Adrienne Sands, University of Minnesota 
Mon May 06 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113On localizing and concentrating of electromagnetic fields YiHsuan Lin, University of Jyvaskyla Abstract:We consider field localizing and concentration of electromagnetic waves governed by the timeharmonic anisotropic Maxwell system in a bounded domain. It is shown that there always exist certain boundary inputs which can generate electromagnetic fields with energy localized/concentrated in a given subdomain while nearly vanishing in another given subdomain. The theoretical results may have potential applications in telecommunication, inductive charging and medical therapy. We also derive a related Runge approximation result for the timeharmonic anisotropic Maxwell system with partial boundary data. 
Mon May 06 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon May 06 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon May 06 
IMA Data Science Lab Seminar1:25pm  Lind 305Robust Accelerated Gradient Methods Mert Gurbuzbalaban, Rutgers, The State University Of New Jersey Abstract:We study the problem of minimizing a strongly convex and smooth function when we have noisy estimates of its gradient. We propose a novel multistage accelerated algorithm that is universally optimal in the sense that it achieves the optimal rate both in the deterministic and stochastic case and operates without knowledge of noise characteristics. The algorithm consists of stages that use a stochastic version of Nesterov's accelerated algorithm with a specific restart and parameters selected to achieve the fastest reduction in the biasvariance terms in the convergence rate bounds. Mert Gürbüzbalaban is an assistant professor at Rutgers University. Previously, he was a postdoctoral associate at the Laboratory for Information and Decision Systems (LIDS) at MIT. He is broadly interested in optimization and computational science driven by applications in largescale information and decision systems. He received his B.Sc. degrees in Electrical Engineering and Mathematics as a valedictorian from Bo?aziçi University, Istanbul, Turkey, the Diplôme dingénieur degree from École Polytechnique, France, and the M.S. and Ph.D. degrees in (Applied) Mathematics from the Courant Institute of Mathematical Sciences, New York University. Dr. Gürbüzbalaban received the Kurt Friedrichs Prize (given by the Courant Institute of New York University for an outstanding thesis) in 2013, Bronze Medal in the École Polytechnique Scientific Project Competition in 2006, the Nadir Orhan Bengisu Award (given by the electricalelectronics engineering department of Bo?aziçi University to the best graduating undergraduate student) in 2005 and the Bülent Kerim Altay Award from the ElectricalElectronics Engineering Department of Middle East Technical University in 2001. He received funding from a variety of sources including multiple programs at the U.S. National Science Foundation. 
Fri May 03 
First Year Seminar5:30pm  Vincent 364First Year Seminar TBA 
Fri May 03 
Combinatorics Seminar3:35pm  Vincent Hall 570Combinatorics of cluster structures in Schubert varieties Melissa ShermanBennett, UC Berkeley/Harvard Abstract:The (affine cone over the) Grassmannian is a prototypical example of a variety with "cluster structure"; that is, its coordinate ring is a cluster algebra. Scott (2006) gave a combinatorial description of this cluster algebra in terms of Postnikov's plabic graphs. It has been conjectured essentially since Scott's result that Schubert varieties also have a cluster structure with a description in terms of plabic graphs. I will discuss recent work with K. Serhiyenko and L. Williams proving this conjecture. The proof uses a result of Leclerc, who shows that many Richardson varieties in the full flag variety have cluster structure using clustercategory methods, and a construction of Karpman to build plabic graphs for each Schubert variety. Time permitting, I will also discuss our results on cluster structures on a larger class of positroid varieties, which involve the combinatorics of "generalized" plabic graphs. 
Fri May 03 
Lie Theory Seminar2:30pm  Vincent Hall 6Lie Theory Seminar 
Fri May 03 
Probability Seminar2:30pm  Vincent Hall 213The majority vote process on trees: convergence to equilibrium Larry Gray, UMN Abstract:This is joint with Maury Bramson, who introduced our work last week and then spoke more particularly about the existence of uncountably many mutually singular equilibria in the majority vote process on a tree of vertex degree 5 and higher, whenever the noise rate is sufficiently small. Each equilibrium is associated with a different fixed point of the majority vote operation. Natural question: If the system starts at (or near) one of these fixed points and the noise rate is small, does it converge to the corresponding equilibrium, and if so, how fast? Answering this question can tell us much about the properties of these equilibria, but standard techniques do not apply. I will describe a new method, based on the "graphical construction" of these systems, which shows exponentially quick convergence to equilibrium when the noise rate is sufficiently small. These methods apply to other models on trees, such as the stochastic Ising model, for which the convergence result was previously unknown. This lecture is selfcontained; essential features from the previous week will be included (with some new pictures). 
Fri May 03 
1:25pm  Lind 305 Startup vs. BigCo: Industry Experiences Compared Ben Peirce, Samsung Research America Abstract:Choosing a career path in industry after spending years in academia can be daunting, particularly when deciding between working for a large company or a startup. In this talk, I'll discuss my experiences in both environments, and consider the pros and cons of each for people with more theoretical backgrounds. Ben Peirce is Sr. Director of Development at Samsung Research America in Mountain View, CA, where his team builds analytics tools for mobile software services. He joined Samsung in 2018 through the acquisition of his virtual reality analytics startup, Vrtigo, where he served as CEO. Prior to cofounding Vrtigo, Ben spent a decade building analytics systems at several startups as either founder or early employee. He has a Ph.D. in engineering and S.M. in applied mathematics from Harvard, where he studied control theory and robotics, and a B.M.E. from the University of Minnesota. 
Fri May 03 
Ordway Lecture Series1:25pm  Vincent Hall 301Representations of Real Reductive Groups Professor Kari Vilonen, University of Melbourne 
Fri May 03 
Probability Seminar9:30am CANCELLED 
Thu May 02 
Colloquium3:35pm  Vincent Hall 16Singularity Formation in 3D Euler Equations and Related Models Thomas Hou, Ordway Vsitor, Caltech Abstract:Whether the 3D incompressible Euler equations can develop a finite time singularity from smooth initial data is a longstanding open question in mathematical fluid dynamics. Recent computations have provided strong numerical evidence that the 3D Euler equations develop a finite time singularity from smooth initial data. I will report some recent progress in providing a rigorous justification of the singularity formation in the 3D Euler equations and related models. 
Thu May 02 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu May 02 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu May 02 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Commutative Algebra Seminar 
Thu May 02 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu May 02 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Thu May 02 
Student Number Theory Seminar11:00am  Vincent Hall 213Introduction to Langlands philosophy Dev Hedge, University of Minnesota Abstract:We will give less precise but hopefully very motivational introduction to Langlands philosophy with many examples. A serious background in anything is not essential. 
Thu May 02 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed May 01 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Wed May 01 
AMS Intro to Research Seminar5:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed May 01 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Jordan form data from the perspective of the derived category Peter Webb, University of Minnesota Abstract:We show that certain sets of representations of Dynkin quivers are determined by their Jordan form data. The description is phrased in terms of the bounded derived category of representations of the quiver. This continues the study of the paper of Garver, Patrias and Thomas: Minuscule reverse plane partitions via quiver representations. 
Wed May 01 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Wed May 01 
Ordway Lecture Series1:25pm  Vincent Hall 301Representations of Real Reductive Groups Professor Kari Vilonen, University of Melbourne 
Tue Apr 30 
Colloquium3:35pm  Vincent Hall 16The NTRU Class of cryptosystems, lattices, and post quantum cryptography Jeffrey Hoffstein, Brown University Abstract:I'll discuss the nature and origins of public key cryptography, and the dangers that the development of quantum computers pose to the security of the internet and virtually all cryptosystems presently in widespread use. All public key cryptographic systems are based on a hard mathematical problem, and I'll explain how, while originally despised, hard problems based on lattices have evolved to become the most promising direction for the development of quantum resistant cryptography. I'll focus on NTRU, the earliest effective and efficient public key cryptosystem, which was developed in 1996 by myself, Jill Pipher and Joe Silverman. I will also discuss the recent history of public key cryptography. The talk will require no previous knowledge of lattices or cryptography, and will be aimed at a wide audience. 
Tue Apr 30 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Apr 30 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Apr 30 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Mon Apr 29 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Mon Apr 29 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Mon Apr 29 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Applied and Computational Mathematics Seminar 
Mon Apr 29 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon Apr 29 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Apr 29 
IMA Data Science Lab Seminar1:25pm  Lind 305Solving Multiscale Problems with Subsampled Data by Integrating PDE Analysis with Data Science Thomas Hou, California Institute of Technology Abstract:In many practical applications, we often need to provide solutions to quantities of interest to a largescale problem but with only subsampled data and partial information of the physical model. Traditional PDE solvers cannot be used directly for this purpose. On the other hand, many powerful techniques have been developed in data science to represent and compress data for useful information. A crucial factor for the success of these methods is to exploit some low rank or sparsity structures in these highdimensional data. In this talk, we will describe our recent effort in developing effective numerical methods to solve multiscale problems using subsampled data. The PDE analysis will help reveal certain important solution structures so that we can use techniques from data science to give accurate approximations for these quantities of interest. Thomas Yizhao Hou is the Charles Lee Powell professor of applied and computational mathematics at Caltech. His research interests are centered around developing mathematical analysis and effective computational methods for vortex dynamics, interfacial flows, multiscale problems and data analysis. He received his Ph.D. in mathematics from UCLA in 1987, and joined the Courant Institute as a junior faculty member in 1989. He moved to Caltech in 1993 and was named the Charles Lee Powell Professor in 2004. He was the founding EditorinChief of the SIAM Journal on Multiscale Modeling and Simulation from 2002 to 2007 and served on the IMA Board of Governors from 2010 to 2014. Dr. Hou is a Fellow of American Academy of Arts and Sciences, a SIAM Fellow and an AMS Fellow. 
Mon Apr 29 
Ordway Lecture Series1:25pm  Vincent Hall 301Representations of Real Reductive Groups Professor Kari Vilonen, University of Melbourne 
Fri Apr 26 
First Year Seminar5:30pm  Vincent 364First Year Seminar TBA 
Fri Apr 26 
Lie Theory Seminar3:35pm  Vincent Hall 6Lie Theory Seminar 
Fri Apr 26 
Combinatorics Seminar3:35pm  Vincent Hall 570Generalized BottSamelson resolutions for Schubert varieties Eric Sommers, UMass Amherst Abstract:This talk focuses on generalized BottSamelson resolutions of Schubert varieties. These resolutions are iterated G/Pbundles (for different parabolic subgroups P of the algebraic group G). Special cases have appeared in the work of Zelevinsky, Wolper, Ryan and several other authors. After introducing these resolutions and some of their properties, we discuss a possible best resolution for a given Schubert variety X(w), based on a combinatorial condition on the inversion set of the Weyl group element w. If time permits, we will discuss a computer program that calculates local intersection cohomology (i.e., KazhdanLusztig polynomials) from these resolutions. This is joint work with Jennifer Koonz. 
Fri Apr 26 
Ordway Lecture Series3:35pm  Vincent Hall 6New examples of Euler systems Ordway Visitor Christopher Skinner, Princeton University Abstract:In this talk we will describe a number of new Euler systems and especially try to explain how the ideas from our 2nd lecture fit in. These new examples include Euler systems for RankinSelberg products for modular forms (due to Lei, Loeffler, and Zerbes), for Siegel modular forms of genus 2, and for products of unitary groups, among others. 
Fri Apr 26 
Probability Seminar2:30pm  Vincent Hall 213Majority vote processes on trees Maury Bramson, UMN Abstract:The majority vote process was one of the first interacting particle systems to be investigated and can be described as follows. There are two possible opinions at each site and that opinion switches randomly to the majority opinion of the neighboring sites. Also, at a different rate epsilon, the opinion at each site randomly changes due to noise. Despite its simple dynamics, the majority vote process is difficult to analyze. In particular, on Z^d with d>1 and epsilon chosen small, it is not known whether there exists more than one equilibrium. This is surprising due to the close analogy between the majority vote process and the Ising model. Here, we discuss work with Larry Gray on the majority vote process on the infinite tree with vertex degree d, where it is shown that, for small noise, there are uncountably many mutually singular equilibria, and that convergence to equilibrium occurs exponentially quickly from nearby initial states. Our methods rely on graphical constructions; they are quite flexible and can be used to obtain analogous results for other models, such as the stochastic Ising model on a tree. This is the first part of a twolecture presentation, and will concentrate on background and on existence of equilibria. Larry Gray will give the second part the following week, which will concentrate on convergence. 
Fri Apr 26 
Special Events and Seminars2:30pm  Vincent Hall 311DRP End of Semester Presentations Abstract:Speaker: 
Fri Apr 26 
Ordway Lecture Series1:25pm  Vincent Hall 301Representations of Real Reductive Groups Professor Kari Vilonen, University of Melbourne 
Fri Apr 26 
Probability Seminar9:30am CANCELLED 
Thu Apr 25 
Colloquium3:35pm  Vincent Hall 16Recent progress on the GanGrossPrasad and IchinoIkeda conjectures for unitary groups Raphael BeuzartPlessis, CNRS and Columbia University Abstract:A celebrated result of Waldspurger from the eighties express the central value of certain basechange Lfunctions for $GL_2$ as toric periods of modular forms or generalizations thereof. In the mid 2000s Gan, Gross and Prasad have formulated conjectural generalizations to higher rank classical groups relating the nonvanishing of central values of certain automorphic Lfunctions to the nonvanishing of certain explicit integrals of automorphic forms that are called 'automorphic periods'. These predictions have been subsequently refined by IchinoIkeda and N.Harris into precise identities relating the two invariants. These conjectures also have local counterparts which concern certain branching laws in the representation theory of real or padic groups. Most of these conjectures have now been established for unitary groups. This talk aims to give an introduction to this circle of ideas and to review recent results on the subject. 
Thu Apr 25 
Special Events and Seminars2:30pm  Vincent Hall570DRP End of Semester Presentations 
Thu Apr 25 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Harmonic surfaces and simple loops Vlad Markovic  Ordway Visitor, Caltech 
Thu Apr 25 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Apr 25 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Commutative Algebra Seminar 
Thu Apr 25 
1:00pm  Walter B28 Test Seminar 
Thu Apr 25 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Apr 25 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Thu Apr 25 
Student Number Theory Seminar11:00am  Vincent Hall 213Applying to Jobs in Number Theory Panel, University of Minnesota Abstract:Come hear recent graduates and current grad students discuss their experiences navigating the job market. This panel is hosted by the Student Number Theory seminar, but all graduate students are welcome to attend. 
Thu Apr 25 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Apr 24 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Wed Apr 24 
AMS Intro to Research Seminar5:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed Apr 24 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Heaps and minuscule posets  coontinuation Victor Reiner, University of Minnesota Abstract:We continue reviewing minuscule weights, their weight posets, and minuscule heaps, with the goal of eventually understanding Section 4 of the paper by Garver, Patrias and Thomas 
Wed Apr 24 
PDE Seminar3:35pm  Vincent Hall 570SERRIN LECTURE  Hydrodynamic stability and coherent structure at high Reynolds number Jacob Bedrossian, Maryland Abstract:In this talk I will discuss recent work towards understanding certain stability questions for incompressible Euler or NavierStokes at high Reynolds number, the regime in which the viscous effects are weak. We will discuss the mechanisms which stabilize the most basic classes of equilbria: vortices and shear flows in 2D NavierStokes/Euler. These stabilization mechanisms, sometimes known as inviscid damping and enhanced dissipation arise from the skewsymmetric transport and the interaction between transport and the weak viscosity. We go on to discuss the roles such dynamics play in 3D, in particular, the manner in which twodimensional stability can influence coherent structures in 3D. First, we discuss the subcritical transition of 3D shear flows  the problem of obtaining quantitative estimates on the basin of stability of classical equilibria and the classification of solutions on the borderline of the stability domain. Second, the dynamics of vortex filaments in the 3D NavierStokes equations, which begins with understanding the localintime wellposedness with certain singular initial data, specifically, vorticity in a scaleinvariant Morrey space of measures (in such a class, one does not have, nor does one expect, a general theory of local wellposedness). Connections to kinetic theory problems arising originally in plasma physics regarding nonlinear Landau damping will be addressed if time permits. 
Wed Apr 24 
Lie Theory Seminar1:25pm  Vincent Hall 301A new proof of the JacquetRallis fundamental lemma Professor Raphael BeuzartPlessis, CNRS and Columbia University Abstract:The JacquetRallis fundamental lemma is a local identity between (relative) orbital integrals which originates from the relative trace formula approach to the GanGrossPrasad conjecture for unitary groups and is a crucial ingredient in the recent results of W. Zhang on this conjecture. It was established soon after its formulation by Z. Yun in positive characteristic using the same geometric ideas as in Ngô's proof of the endoscopic fundamental lemma and transferred to characteristic 0 by J. Gordon by modeltheoretic techniques. In this talk, I will present an alternative proof of this fundamental lemma in characteristic zero which is purely local and based on harmonic analytic tools. We note that a third proof of this fundamental lemma has been recently proposed by W. Zhang through a similar although global argument. 
Tue Apr 23 
Ordway Lecture Series3:35pm  Vincent Hall 16Euler systems and local representation theory Ordway Visitor Christopher Skinner, Princeton University Abstract:Many of the known examples of Euler systems come from special cycles on Shimura varieties. So algebraic groups are not far in the background. In this talk we will explain how some of the important properties of these Euler systems can be interpreted in terms of the representation theory of the corresponding groups. 
Tue Apr 23 
Special Events and Seminars3:30pm  Vincent Hall 364Vortex filaments in the 3D NavierStokes equations Jacob Bedrossian, Maryland Abstract:We consider solutions of the NavierStokes equations in 3d with vortex filament initial data of arbitrary circulation, that is, initial vorticity given by a divergencefree vectorvalued measure of arbitrary strength supported on a smooth curve. First, we prove global wellposedness for perturbations of the Oseen vortex column in scalingcritical spaces. Second, we prove local wellposedness (in a sense to be made precise) when the filament is a smooth, closed, nonselfintersecting curve. Besides their physical interest as a model for the coherent vortex filament structures observed in 3d fluids, these results are the first to give wellposedness (in a certain sense) in a neighborhood of large selfsimilar solutions of 3d NavierStokes, as well as solutions which are locally approximately selfsimilar. Joint work with Pierre Germain and Benjamin HarropGriffiths. 
Tue Apr 23 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Apr 23 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Selfhomeomorphisms of reducible 3manifolds and applications in topology, geometry and dynamics. Christoforos Neofytidis, University of Geneva Abstract:We recall the selfhomeomorphisms of a closed oriented reducible 3manifold. Using this description, we discuss various problems in lowdimensional topology and dynamics, such as the existence of Anosov tori in 3manifolds (joint work with Shicheng Wang), the simplicial volume of mapping tori of 3manifolds (joint work Michelle Bucher) and the virtual Betti numbers of mapping tori of 3manifolds. 
Tue Apr 23 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Apr 23 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Mon Apr 22 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Mon Apr 22 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Classical properties of Epstein zeta functions Adrienne Sands, University of Minnesota Abstract:Adrienne Sands of U of MN will continue on "Classical properties of Epstein zeta functions 
Mon Apr 22 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Applied and Computational Mathematics Seminar 
Mon Apr 22 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon Apr 22 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Apr 22 
IMA Data Science Lab Seminar1:25pm  Lind 305How Hard is it to Fool a Neural Net? A Mathematical Look at Adversarial Examples Tom Goldstein, University of Maryland Abstract:Neural networks solve complex computer vision problems with humanlike accuracy. However, it has recently been observed that neural nets are easily fooled and manipulated by "adversarial examples," in which an attacker manipulates the network by making tiny changes to its inputs. In this talk, I give a highlevel overview of adversarial examples, and then discuss a newer type of attack called "data poisoning," in which a network is manipulated at train time rather than test time. Then, I explore adversarial examples from a theoretical viewpoint and try to answer a fundamental question: "Are adversarial examples inevitable?" Tom is an Assistant Professor at University of Maryland. His research lies at the intersection of optimization and distributed computing, and targets applications in machine learning and image processing. He designs optimization methods for a wide range of platforms. This includes powerful cluster/cloud computing environments for machine learning and computer vision, in addition to resource limited integrated circuits and FPGAs for realtime signal processing. Before joining the faculty at Maryland, he completed his PhD in Mathematics at UCLA, and was a research scientist at Rice University and Stanford University. He has been the recipient of several awards, including SIAMs DiPrima Prize, a DARPA Young Faculty Award, and a Sloan Fellowship. 
Fri Apr 19 
First Year Seminar5:30pm  Vincent 364First Year Seminar TBA 
Fri Apr 19 
MCFAM Seminar5:30pm  Vincent Hall 162019 MFM Modeling Workshop Presentations Yield Curve Construction and Valuation and Replication Strategies for Variance Derivatives 2019 FM Modeling Workshop Student Presenters, University of Minnesota Abstract:Two Teams of MFM students from the 2019 MFM Modeling Workshp will present their work to the Seminar. Each group will take a half hour to cover their topics, including Q & A Yield Curve Construction: Calculating the present value of future cash flows is a crucial task for any trading desk. We will explore yield curve bootstrapping and interpolation techniques used to value financial instruments in a consistent framework. The pros and cons of each method will become apparent, and we will converge on an optimal technique that is consistent with major trading desks. Finally, we will see how the financial crisis changed yield curve construction, and fundamentally altered the way we think of the valuing future cash flows. Valuation and Replication Strategies for Variance Derivatives:Variance derivatives have played a major role in the financial markets since the 1990s, as they provide pure exposure to volatility without other added effects. A primary instrument is variance swaps. In this project the participants will explore traditional theory of valuing variance swaps, and their continuous and discrete replication with vanilla derivatives. The connections among variance, volatility swaps, and VIX derivatives will be drawn, alongside examining nonparametric variance swap replication approaches. 
Fri Apr 19 
Combinatorics Seminar3:35pm  Vincent Hall 570K polynomials and matroids Andrew Berget, Western Washington University Abstract:This talk is my about 2009 UMn PhD thesis problem which I have finally solved, only 10 years after the fact. The setup was to take n vectors, tensor them together in n! ways, and consider their span as a representation of the symmetric group Sn. The problem was to see if the character of this representation could be determined knowing only the matroid of the n starting vectors. In this talk I present an affirmative solution to this problem, including an explicit generating function that computes the character from the matroid. The long overdue solution took a lengthy detour through representation theory, algebraic geometry and, fusing the two, equivariant Ktheory. I will keep the technical aspects to a minimum, and focus on explaining how this problem in combinatorics led to a tractable geometric problem. 
Fri Apr 19 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Apr 19 
Probability Seminar2:30pm  Vincent Hall 213Optimal Spectral Shrinkage and PCA with Heteroscedastic Noise Will Leeb, UMN Abstract:I will present recent results on the related problems of denoising, covariance estimation, and principal component analysis for the spiked covariance model with heteroscedastic noise. Specifically, I will present an estimator of the principal components based on whitening the noise, and optimal spectral shrinkers for use with these estimated principal components. I will also show new results on the optimality of whitening for principal subspace estimation. This is joint work with Elad Romanov of the Hebrew University. 
Fri Apr 19 
Probability Seminar9:30am CANCELLED 
Thu Apr 18 
Colloquium3:35pm  Vincent Hall 16Teichmueller flow and complex geometry of Moduli Spaces Vlad Markovic  Ordway Visitor, Caltech Abstract:I will explain why in general the Caratheodory and Teichmueller metrics do not agree on Teichmueller spaces and why this yields a proof of the convexity conjecture of Siu. Moreover, I will illustrate how deep theorems in Teichmueller dynamics play an important role in classifying Teichmueller discs where the two metrics agree. 
Thu Apr 18 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Apr 18 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry 
Thu Apr 18 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Commutative Algebra Seminar 
Thu Apr 18 
Ordway Lecture Series1:25pm  Vincent Hall 113An introduction to Euler systems Ordway Visitor Christopher Skinner, Princeton University Abstract:The breakthrough work of Kolyvagin on the Birch and SwinnertonDyer conjecture introduced the `method of Euler systems.' Euler systems  when known to exist  remain one of the most effective tools for studying class groups and Selmer groups and their relations to special values of Lfunctions. This is an area that has had a recent resurgence of activity, which we hope to describe in these talks. This talk will be an introduction to Euler systems and their main features. 
Thu Apr 18 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Apr 18 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Thu Apr 18 
Student Number Theory Seminar11:00am  Vincent Hall 213More YangBaxter Equations for Metaplectic Ice Claire Frechette, University of Minnesota Abstract:In preparation for my oral exam, I will extend the existing connections between quantum groups and the study of spherical Whittaker models on metaplectic covering groups of GL(r,F), for F a nonarchimedean local field. Brubaker, Buciumas, and Bump showed that for a certain metaplectic nfold cover of GL(r,F) a set of YangBaxter equations govern the behavior of the Whittaker functions and that these equations arise from a Drinfeld twist of a quantum affine Lie superalgebra. I will extend their results to all metaplectic covers of GL(r,F), showing that the same YangBaxter equations underlie the scattering matrix for the Whittaker functions over an nQfold metaplectic cover, where nQ is an integer determined by the cover, and that these equations arise from Drinfeld twists of quantum groups. (I will also define what most of these words mean.) 
Thu Apr 18 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Apr 17 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Wed Apr 17 
AMS Intro to Research Seminar5:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed Apr 17 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Heaps and minuscule posets Victor Reiner, University of Minnesota Abstract:We review minuscule weights, their weight posets, and minuscule heaps, with the goal of eventually understanding Section 4 of the paper by Garver, Patrias and Thomas. 
Wed Apr 17 
PDE Seminar3:35pm  VinH 213PDE Seminar 
Wed Apr 17 
PDE Seminar3:35pm  Vincent Hall 570On some recent results of Collisional Plasma in bounded domains Chanwoo Kim, University of Wisconsin Abstract:In this talk we discuss VlasovPoissonBoltzmann system in bounded domains. Some recent results on regularity and large time behavior of solutions will be presented. 
Tue Apr 16 
Colloquium3:35pm  Vincent Hall 16What's known about the Birch and SwinnertonDyer Conjecture Ordway Visitor Christopher Skinner, Princeton University Abstract:The celebrated Birch and SwinnertonDyer (BSD) Conjecture connects the structure of the rational points on an elliptic curve defined over the rationals to the analytic properties of its associated HasseWeil Lfunction. This talk will recall the BSD conjecture (and its various parts) and related conjectures and survey some of the known results toward them, especially recent work. This talk is intended for a general mathematical audience: no prior acquaintance with elliptic curves or even nonelementary number theory will be assumed. 
Tue Apr 16 
Dynamical Systems2:30pm  Vincent Hall 313The Origins of the Reaction Zone in Microtornado Experiments Patrick Shipman, Colorado State University Abstract:In experimental systems involving diffusing and convecting vapors that react to form solid particulates, a complex sequence of nucleation and growth reactions produces pulsing charged crystals, oscillating fronts, and patterns such as beautiful 3dimensional structures that we call microtornadoes, microstalagtites, and microhurricanes. We will review the rich history of these experiments, starting with a counterdiffusional experiment that figures in the pioneering work on diffusion of Dalton, Graham, Fick, and Stefan. Mathematical analysis will progress from a reactiondiffusion model for the origins of the initial reaction zone, to an analysis of oscillations and particle size distributions, to a fluid dynamical model. The insights carry over to similar structures in protein crystallization experiments and the formation of periodic structures in plants. 
Tue Apr 16 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Apr 16 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Mon Apr 15 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Mon Apr 15 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207The theorem of DixmierMalliavin and a question of Casselman Dev Hegde, U of MN 
Mon Apr 15 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Applied and Computational Mathematics Seminar 
Mon Apr 15 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon Apr 15 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Apr 15 
IMA Data Science Lab Seminar1:25pm  Lind 305Recent Advances in Wasserstein Distributionally Robust Optimization Rui Gao, The University of Texas at Austin Abstract:In this talk, we consider decisionmaking problems under data uncertainty. In particular, we study a framework, called Wasserstein distributionally robust optimization, that aims to find a decision that hedges against a set of distributions that are close to some nominal distribution in Wasserstein metric. This framework, although being an infinite dimensional optimization, has a finitedimensional tractable reduction in various datadriven settings by virtue of duality, and is closely related to many regularization problems in statistical learning. I will discuss the generalization error bound and asymptotic properties of such framework, and compare it with other distributional uncertainty sets including divergencebased and momentbased sets. If time permits, I will talk about an application of the framework to robust classification with limited information. Rui Gao is an Assistant Professor of Information, Risk, and Operations Management at the McCombs School of Business at the University of Texas at Austin. He received his Ph.D. in Operations Research from Georgia Institute of Technology in 2018. His current research interests lie in the intersection of decisionmaking under uncertainty and statistical learning, as well as their applications in data analytics. His work has been recognized with several INFORMS prize, including finalist in Nicholson student paper competition in 2016, runnerup in the Computing Society student paper prize in 2017, and winner of the Data Mining best paper award in 2017. 
Fri Apr 12 
MCFAM Seminar5:30pm  Murphy Hall 130Model Development & Delivery in Real World Quant Finance Florian Huchede, Director & FX Lead Quant  CME Group Abstract:Over the last 10 years, financial companies have been increasingly using quantitative models for decision making. Well performing models can provide automatic and objective decision making as well as a certain ability to synthesize complex issues. However, models expose companies to model risk, higher development cost and longer delivery time. In this MCFAM seminar, we will cover how to reduce the model risk and time to market by using a model design process. Furthermore, we will apply the process on a particular example: OTC FX option volatility calibration. Bio: Florian Huchedé is a Director of Quantitative Risk Management at CME Group. He leads an international team of quantitative analysts that work on designing, implementing and filing quantitative algorithms on various applications (settlement, pricing, data cleansing, risk management, product creation and large optimization). Furthermore, he is the lead quant for the FX and Equity asset classes. Florian graduated from the Financial Mathematics program at University of Chicago (2010). He completed his undergraduate studies and MS in Engineering at Ecole Francaise dElectronique et dInformatique in Paris, France (2007). Prior to joining CME Group, he worked at Credit Agricole Asset Management Alternative Investment and at The Option Clearing Corporation. With more than 10 years of experience, Florian is focused on innovation, creativity and giving back to the quant community. He holds three U.S. patents on risk management and financial products. Furthermore, he initiated a joint research program between University of Chicago and CME Group in 2012. Since then, the program has expanded and is being utilized by many other companies. 
Fri Apr 12 
First Year Seminar5:30pm  Vincent 364First Year Seminar TBA 
Fri Apr 12 
Lie Theory Seminar3:35pm  Vincent Hall 313Lie Theory Seminar 
Fri Apr 12 
Combinatorics Seminar3:35pm  Vincent Hall 570Some congruences for sums of binomial coefficients Moa Apagodu, Virginia Commonwealth University Abstract:In a recent beautiful but technical article, William Y.C. Chen, QingHu Hou, and Doron Zeilberger developed an algorithm for finding and proving congruence identities (modulo primes) of indefinite sums of many combinatorial sequences, namely those (like the Catalan and Motzkin sequences) that are expressible in terms of constant terms of powers of Laurent polynomials. We first give a leisurely exposition and then extend it in two directions. The Laurent polynomials may be of several variables, and instead of single sums we have multiple sums. 
Fri Apr 12 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Apr 12 
1:25pm  Lind 305 Stating the Obvious  Job Search to Analytics Leadership Sandhya Surapanenii, Stratasys Abstract:From "is networking really important" to "do hiring managers read cover letters", from "why should data exploration begin with a question" to "how to build a culture of data driven decision making", we have heard it all many, many times. But these are questions that warrant a reminder. And another. And another. I hope to be that person and remind you of a few key strategies to employ in job search and best practices to avoid pitfalls in the business world. I will share failures and lessons from my experience in data management and analytics, as well as decode marketing function. Sandhya Surapaneni (aka Sandy) works as a Global Marketing Analytics Leader at Stratasys, a pioneer in 3D printing technology. Her current focus is on building a foundation in analytics to integrate datadriven insights into every day business decisions that align with the company's long term strategy. Prior to joining Stratasys, Sandy worked as a Database Lead at BI Worldwide, building and supporting the data layer of several web applications. Sandy has a M.S in Computer Science from the University of Texas at Arlington and a M.S in Business Analytics from Carlson School of Management. Born and raised in India, she has been a Minneapolis resident for 13 years and enjoys its lakes and coffee shops. 
Fri Apr 12 
Probability Seminar9:30am CANCELLED 
Thu Apr 11 
Special Events and Seminars2:30pm  Vincent Hall 570Informal Fluids Seminar with the speaker Samuel PunshonSmith Samuel PunshonSmith 
Thu Apr 11 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Apr 11 
Commutative Algebra Seminar1:25pm  Vincent Hall 301SemiAmple Asymptotic Syzygies Juliette Bruce Abstract:I will discuss the asymptotic nonvanishing of syzygies for products of projective spaces, generalizing the monomial methods of EinErmanLazarsfeld. This provides the first example of how the asymptotic syzygies of a smooth projective variety whose embedding line bundle grows in a semiample fashion behave in nuanced and previously unseen ways. 
Thu Apr 11 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Apr 11 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Thu Apr 11 
Student Number Theory Seminar11:00am  Vincent Hall 213Student Number Theory Seminar 
Thu Apr 11 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Apr 10 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Wed Apr 10 
AMS Intro to Research Seminar5:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed Apr 10 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Reflection functors and nilpotent endomorphisms  continuation Dongkwan Kim, University of Minnesota Abstract:We describe how the Jordan form data of quiver representations interact with reflection functors, continuing with the paper of Garver, Patrias and Thomas: Minuscule reverse plane partitions via quiver representations. 
Wed Apr 10 
PDE Seminar3:30pm  Vincent Hall 570Lagrangian chaos and scalar mixing in stochastic fluid mechanics Samuel PunshonSmith, Brown University Abstract:Lagrangian chaos refers to the chaotic behavior of 
Wed Apr 10 
Special Events and Seminars2:30pm  Vincent Hall 213Arithmetic level raising for unitary groups and BeilinsonBlochKato conjecture (II) Yifeng Liu, Yale University Abstract:In this series of two talks, we will introduce the recent progress on BeilinsonBlochKato conjecture for RankinSelberg motives of arbitrary rank. We will discuss an important technique used in the proof, namely, the arithmetic level raising for unitary groups of even rank. We will also mention other interesting results we obtained during the course of proof. This is based on a joint work with Y. Tian, L. Xiao, W. Zhang, and X. Zhu 
Tue Apr 09 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Apr 09 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Apr 09 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Tue Apr 09 
Special Events and Seminars11:00am  Vincent Hall 213Arithmetic level raising for unitary groups and BeilinsonBlochKato conjecture (I) Yifeng Liu, Yale University Abstract:In this series of two talks, we will introduce the recent progress on BeilinsonBlochKato conjecture for RankinSelberg motives of arbitrary rank. We will discuss an important technique used in the proof, namely, the arithmetic level raising for unitary groups of even rank. We will also mention other interesting results we obtained during the course of proof. This is based on a joint work with Y. Tian, L. Xiao, W. Zhang, and X. Zhu. 
Mon Apr 08 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Mon Apr 08 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Classical properties of Epstein zeta functions Adrienne Sands, University of Minnesota 
Mon Apr 08 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Applied and Computational Mathematics Seminar 
Mon Apr 08 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon Apr 08 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Apr 08 
IMA Data Science Lab Seminar1:25pm  Lind 305A Brief Overview of Quantum Computing Vlad Pribiag, University of Minnesota, Twin Cities Abstract:Quantum computing has been receiving rapidlygrowing interest from both industry and government funding agencies in the last several years. In this talk, I will provide an introduction to the key concepts of quantum mechanics as related to quantum computing, and will then outline several areas were quantum computers could make substantial contributions not accessible to classical computers. I will also provide an overview of leading approaches for developing the building blocks of future quantum computers, including work from our lab. 
Fri Apr 05 
First Year Seminar5:30pm  Vincent 364First Year Seminar TBA 
Fri Apr 05 
Combinatorics Seminar3:35pm  Vincent Hall 570Topological combinatorics of crystal posets Molly Lynch, North Carolina State University Abstract:Crystal bases were first introduced by Kashiwara when studying modules of quantum groups. Each crystal base has an associated directed, edge colored graph called a crystal graph. In many cases, these crystal graphs give rise to a natural partial order. In this talk, we study crystal posets associated to highest weight representations. We use lexicographic discrete Morse functions to connect the Möbius function of an interval in a crystal poset with the relations that exist among crystal operators within that interval. We will discuss some further directions for this work. 
Fri Apr 05 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Apr 05 
Probability Seminar2:30pm  Vincent Hall 213Frog model on trees with drift Si Tang, Lehigh University Abstract:We provide a uniform upper bound on the minimal drift so that the onepersite frog model on a dary tree is recurrent. To do this, we introduce a subprocess that couples across trees with different degrees. Finding couplings for frog models on nested sequences of graphs is known to be difficult. The upper bound comes from combining the coupling with a new, simpler proof that the frog model on a binary tree is recurrent when the drift is sufficiently strong. This is a joint work with E. Beckman, N. Frank, Y. Jiang, and M. Junge. 
Fri Apr 05 
Probability Seminar9:30am CANCELLED 
Thu Apr 04 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Apr 04 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Apr 04 
Commutative Algebra Seminar1:25pm  Vincent Hall 301An Analogue of the HartshornePolini Theorem in Positive Characteristic Zhang Wenliang, University of Illinois at Chicago Abstract:Recently, Hartshorne and Polini proved a theorem to characterize the 
Thu Apr 04 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Apr 04 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Thu Apr 04 
Student Number Theory Seminar11:00am  Vincent Hall 213On congruence properties of Ramanujan tau function Dev Hegde, University of Minnesota Abstract:Serre and SwinnertonDyer reproved many congruence relations around 1970 for the Ramanujan tau function by reinterpreting the relations in terms of ladic representations. We will give an introduction to this topic. 
Thu Apr 04 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Apr 03 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Wed Apr 03 
AMS Intro to Research Seminar5:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed Apr 03 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Reflection functors and nilpotent endomorphisms Dongkwan Kim, University of Minnesota Abstract:We describe how the Jordan form data of quiver representations interact with reflection functors, continuing with the paper of Garver, Patrias and Thomas: Minuscule reverse plane partitions via quiver representations. 
Wed Apr 03 
PDE Seminar3:30pm  Vincent Hall 570Convexity of Whitham's highest cusped wavear Bruno Vergara, Madrid Abstract:Whitham's model of shallow water waves is a nonlocal dispersive equation that features traveling wave solutions and also singularities. I will discuss a conjecture of Ehrnström and Wahlén on the profile of solutions of extreme form and show that there exists a highest, cusped and periodic solution convex between consecutive crests of $C^{1/2}$regularity. The talk is based on joint work with A. Enciso and J. GómezSerrano. 
Tue Apr 02 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Apr 02 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Apr 02 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Mon Apr 01 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Mon Apr 01 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Classical facts about Epstein zeta functions Adrienne Sands, University of Minnesota 
Mon Apr 01 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Applied and Computational Mathematics Seminar 
Mon Apr 01 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Quadratic Wasserstein Metrics for Nonlinear Inverse Problems Kui Ren, Columbia University Abstract:In the absence of analytical reconstruction methods, numerical solutions of nonlinear inverse problems have been mostly based on leastsquare formulations where solutions are sought by minimizing the $L^2$ difference between model predictions and measured data. We present here recent computational studies of some nonlinear inverse problems where quadratic Wasserstein distances are used to measure the discrepancy between model predictions and measured data. Related numerical and theoretical issues will be discussed. 
Mon Apr 01 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Apr 01 
IMA Data Science Lab Seminar1:25pm  Lind 305How to Deal with Big Data? Understanding Largescale Distributed Regression Edgar Dobriban, Wharton School of the University of Pennsylvania Abstract:Modern massive datasets pose an enormous computational burden to practitioners. Distributed computation has emerged as a universal approach to ease the burden: Datasets are partitioned over machines, which compute locally, and communicate short messages. Distributed data also arises due to privacy reasons, such as with medical databases. It is important to study how to do statistical inference and machine learning in a distributed setting. In this talk, we present results about onestep parameter averaging in statistical linear models under data parallelism. We do linear regression on each machine, and take a weighted average of the parameters. How much do we lose compared to doing linear regression on the full data? Here we study the performance loss in estimation error, test error, and confidence interval length in high dimensions, where the number of parameters is comparable to the training data size. We discover several key phenomena. First, averaging is not optimal, and we find the exact performance loss. Second, different problems are affected differently by the distributed framework. Estimation error and confidence interval length increases a lot, while prediction error increases much less. These results match numerical simulations and a data analysis example. To derive these results, we rely on recent results from random matrix theory, where we also develop a new calculus of deterministic equivalents as a tool of broader interest. Edgar Dobriban is an assistant professor of statistics at the Wharton School of the University of Pennsylvania. He obtained his PhD in Statistics in 2017 from Stanford University, advised by David Donoho, and his undergraduate degree in mathematics from Princeton University in 2012. His research interests are in developing statistical methods and theory for largescale data analysis. 
Fri Mar 29 
First Year Seminar5:30pm  Vincent 364First Year Seminar TBA 
Fri Mar 29 
MCFAM Seminar5:30pm  Vincent Hall 16MFM Modeling Workshop Presentations  Machine Learning in Equity Classification and Smart Beta Investing in Commodities 2019 FM Modeling Workshop Student Presentations, University of Minnesota Abstract:Two Teams of MFM students from the 2019 MFM Modeling Workshop will present their work to the Seminar. Each group will take a half hour to cover their topics, including Q & A Machine Learning in Equity Classification: This MFM modeling workshop team worked with various machine learning classification models with the goal of classifying equities via wellknown quantitative factors such as Value and Momentum. The classification was supervised, utilizing a novel ETF dataset which was supplemented extensively. The team worked in Python, especially the Scikit Learn module. They will present their project to seminar attendees Smart Beta Investing in Commodities: Ever since the first stocks and bonds were issued by the Dutch East India Company (VOC), investors have tried to understand what drives returns. Smart Beta strategies have gained popularity lately by offering the potential for betterthanmarket returns with betterdefined risks, especially after the recognition in 2008 that multiasset classes can experience severe losses at the same time despite their apparent intrinsic differences. Smart beta strategies can take many different forms, with a variety of objectives. They can simply aim at reducing risks (the riskbased approach) or enhancing return through exposure to systematic factors (the factorbased approach). In commodities investing, alternative index movement was born from frustration with the inherent biases of conventional indices. For example, negative commodity roll yields can erode returns by as much as 50%. This team explored the opportunities of constructing a commodity investment portfolio that uses different smart beta approaches to seek enhancing returns and risk reduction. Factors like curve, value, and momentum were examined in the backtest. 
Fri Mar 29 
Combinatorics Seminar3:35pm  Vincent Hall 570A combinatorial duality and the Sperner property for the weak order Christian Gaetz, MIT Abstract:A poset is Sperner if its largest antichain is no larger than its largest rank. In the 1980's, Stanley used the HardLefschetz Theorem to prove the Sperner property for strong Bruhat orders on Weyl groups. I will describe joint work with Yibo Gao in which we prove Stanley's conjecture that the weak Bruhat order on the symmetric group is also Sperner, by exhibiting a combinatoriallydefined representation of sl2 respecting the structure of the weak and strong orders. I will explain how this representation gives rise to a combinatorial duality between the weak and strong Bruhat orders and leads to a strong order analogue of Macdonald's reduced word identity for Schubert polynomials. 
Fri Mar 29 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Mar 29 
Probability Seminar2:30pm  Vincent Hall 213Moments of scores Sergey Bobkov, UMN Abstract:If a random variable X has an absolutely continuous 
Fri Mar 29 
1:25pm  Lind 305 So, How Do You Get a Job? Chang Lee, Lowe's Abstract:I was late. I only decided to find a job in industry in the 4th year of my graduate study even though I never had a job outside of academia. The one question that I kept asking was: how do you get a job? It was scary because I did't know what to do. But I ended up getting a job. And today, I think I'm doing fine. If you are about to start on the path to industry but you feel that you are full of questions and doubts, then this talk may be for you. In this talk, I will show you two things: 1. my experience of going into industry, and You will walk away with guidelines and tips that I learned from my mistakes and observations. It will help you save time and avoid frustrations in the process. Chang currently works as a data scientist at Lowe's. He entered into the data science field as an intern for a baseball team, the Tampa Bay Rays. He got his Ph.D in Mathematics from Vanderbilt University in 2017 under Alex Powell. Besides math and data, Chang has become a soul food advocate and survives on barbecue and hot chicken. You can learn more about his experience outside of academia at his blog: https://changhsinlee.com and his YouTube channel: https://youtube.com/c/softwareforscience 
Fri Mar 29 
Probability Seminar9:30am CANCELLED 
Thu Mar 28 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Mar 28 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Mar 28 
Commutative Algebra Seminar1:25pm  Vincent Hall 301BernsteinSato polynomials in positive characteristic and Hodge theory Thomas Bitoun, University of Toronto Abstract:BernsteinSato polynomials are fundamental in Dmodule theory. For 
Thu Mar 28 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Mar 28 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Thu Mar 28 
Student Number Theory Seminar11:00am  Vincent Hall 213On congruence properties of Ramanujan tau function Dev Hegde, University of Minnesota Abstract:Serre and SwinnertonDyer reproved many congruence relations around 1970 for the Ramanujan tau function by reinterpreting the relations in terms of ladic representations. We will give an introduction to this topic. 
Thu Mar 28 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Mar 27 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Wed Mar 27 
AMS Intro to Research Seminar5:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed Mar 27 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Reflection functors Dongkwan Kim, University of Minnesota Abstract:We define the notion of reflection functors between the categories of quiver representations and discuss some of their basic properties. After this, we explain how these functors are related to (generic) Jordan types and corresponding representations of quivers. 
Wed Mar 27 
PDE Seminar3:30pm  Vincent Hall 570PDE Seminar Luis Vega, Serrin Lecture 
Tue Mar 26 
Dynamical Systems2:30pm  Vincent Hall 313Ice issues in conceptual climate models Alice Nadeau, University of Minnesota Abstract:Conceptual climate models are a necessary tool for scientists trying to understand Earth and other rocky planets because they can provide insight on predominant forces affecting a planet's climate. This talk will focus on BudykoSellers type energy balance models, a particular class of conceptual models used to study icealbedo feedback in the climate system. In this talk I will discuss the different ways one can represent ice in these models, including some of my recent results in extending these models to other planets. 
Tue Mar 26 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Mar 26 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar TBA 
Mon Mar 25 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Mon Mar 25 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Mon Mar 25 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Low rankness in forward and inverse kinetic theory Qin Li, University of Wisconsin Abstract:Multiscale kinetic equations can be compressed: in certain regimes, the Boltzmann equation is asymptotically equivalent to the Euler equations, and the radiative transfer equation is asymptotically equivalent to the diffusion equation. A lot of detailed information is lost when a system passes to the limit. In linear algebra, it is equivalent to a system being of low rank. I will discuss such transition and how it affects the computation: mainly, in the forward regime, inserting lowrankness could greatly advances the computation, while in the inverse regime, the system being of low rank typically makes the problems significantly harder. 
Mon Mar 25 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon Mar 25 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Mar 25 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Mark Hsiao, Netflix, Inc 
Fri Mar 22 
First Year Seminar5:30pm  Vincent 364First Year Seminar TBA 
Fri Mar 22 
Combinatorics Seminar3:35pm  Vincent Hall 570Combinatorics Seminar 
Fri Mar 22 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Mar 22 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Mar 22 
Probability Seminar9:30am CANCELLED 
Thu Mar 21 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Mar 21 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Mar 21 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Commutative Algebra Seminar 
Thu Mar 21 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Mar 21 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Thu Mar 21 
Student Number Theory Seminar11:00am  Vincent Hall 213Student Number Theory Seminar 
Thu Mar 21 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Mar 20 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Wed Mar 20 
AMS Intro to Research Seminar5:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed Mar 20 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Algebraic Representation Theory 
Tue Mar 19 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Mar 19 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Mar 19 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Mon Mar 18 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Mon Mar 18 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Mon Mar 18 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Applied and Computational Mathematics Seminar 
Mon Mar 18 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon Mar 18 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Mar 15 
First Year Seminar5:30pm  Vincent 364First Year Seminar TBA 
Fri Mar 15 
Combinatorics Seminar3:35pm  Vincent Hall 570Cell Decompositions for Rank Two Quiver Grassmannians Dylan Rupel, Michigan State University Abstract:A quiver Grassmannian is a variety parametrizing subrepresentations of a given quiver representation. Reineke has shown that all projective varieties can be realized as quiver Grassmannians. In this talk, I will study a class of smooth projective varieties arising as quiver Grassmannians for (truncated) preprojective representations of an nKronecker quiver, i.e. a quiver with two vertices and n parallel arrows between them. The main result I will present is a recursive construction of cell decompositions for these quiver Grassmannians motivated by the theory of rank two cluster algebras. If there is time I will discuss a combinatorial labeling of the cells by which their dimensions may conjecturally be directly computed. This is a report on joint work with Thorsten Weist. 
Fri Mar 15 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Mar 15 
Probability Seminar2:30pm  Vincent Hall 213The generalized TAP free energy WeiKuo Chen, UMN Abstract:Spin glasses are disordered spin systems initially invented by theoretical physicists with the aim of understanding some strange magnetic properties of certain alloys. In particular, over the past decades, the study of the SherringtonKirkpatrick (SK) meanfield model via the replica method has received great attention. In this talk, I will discuss another approach to studying the SK model proposed by ThoulessAndersonPalmer (TAP). I will explain how the generalized TAP correction appears naturally and give the corresponding generalized TAP representation for the free energy. Based on a joint work with D. Panchenko and E. Subag. 
Fri Mar 15 
Special Events and Seminars2:30pm  Vincent Hall 1Mathematical Physics, Algebraic Geometry, and Commutative Algebra Nadia Ott 
Fri Mar 15 
1:25pm  Lind 305 Lecture Karyn Sutton, The Institute for Disease Modeling 
Fri Mar 15 
Probability Seminar9:30am CANCELLED 
Thu Mar 14 
Colloquium3:35pm  Vincent Hall 16ShortTime Asymptotic Methods In Financial Mathematics Jose FigueroaLopez, Washington University Abstract:In this talk, we will be concerned with the average values of certain random functionals of the path of a stochastic process during a given time period. Highorder asymptotic characterizations of such values when the time period shrinks to 0 have a wide range of applications. In statistics, they are instrumental in establishing infill asymptotic properties of highfrequency based statistical methods of stochastic processes. In finance, they have been used as model selection and calibration tools based on near expiration option prices. In some Engineering problems, they also show up as a method to solve a problem in continuous time by looking at the analogous problem in discrete time and shrinking the time step to 0. These shorttime asymptotic methods are especially useful in the study of complex models with jumps and stochastic volatility due to the lack of tractable formulas and efficient statistical and numerical procedures. In this talk, I will discuss some recent advances in the area and illustrate their broad relevance in several contexts. Bio: Dr. FigueroaLópez is a Professor in the Department of Mathematics and Statistics at Washington University in St. Louis. He currently serves as part of the executive committee and the chair of the statistics committee of the Department. Formerly he was Associate Professor of Statistics at Purdue University, where he served as Associate Director of the Computational Finance Program and as a member of the University Senate. Professor Figueroas ongoing research includes shorttime asymptotics of jumpdiffusion models, diffusion limits of Limit Order Book models, optimal limit order placement problems, market making via reinforced learning, and optimal tuning of highfrequency based econometric methods. He was awarded the NSF career award in 2012 and currently has two active NSF grants on the interplay of finance, statistics, and probability. He is an Associate Editor of the SIAM Journal on Financial Mathematics (SIFIN) and a former Associate Editor of Electronic Journal of Statistics. 
Thu Mar 14 
Special Events and Seminars1:25pm  Vincent Hall 113Nearby cycles over general bases and duality Weizhe Zheng, Chinese Academy of Sciences and Princeton University Abstract:Over onedimensional bases, Gabber and Beilinson proved theorems on the commutation of the nearby cycle functor and the vanishing cycle functor with duality. In this talk, I will explain a way to unify the two theorems, confirming a prediction of Deligne. I will also discuss the case of higherdimensional bases and applications to local acyclicity, following suggestions of Illusie and Gabber. This is joint work with Qing Lu. 
Thu Mar 14 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Mar 14 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Towards Free Resolutions Over Scrolls Aleksandra SobieskaSnyder, Texas A&M Abstract:Free resolutions over the polynomial ring have a storied and active 
Thu Mar 14 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Mar 14 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Thu Mar 14 
Student Number Theory Seminar11:00am  Vincent Hall 213Knots and Primes Part II: The Linking Number and Legendre Symbol Katy Weber, University of Minnesota Abstract:We review the analogy between knots in 3manifolds and prime ideals in number rings, and push it further to realize the Legendre symbol as the analogue of the (mod 2) linking number. This talk should be accessible even if you did knot attend seminar last week. 
Thu Mar 14 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Mar 13 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Wed Mar 13 
AMS Intro to Research Seminar5:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed Mar 13 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Postponed Dongkwan Kim, University of Minnesota Abstract:This talk is postponed to March 27. 
Tue Mar 12 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Mar 12 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Mar 12 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Tue Mar 12 
Special Events and Seminars11:00am  Vincent 213Compatible systems along the boundary Weizhe Zheng, Chinese Academy of Sciences and Princeton University Abstract:A theorem of Deligne says that compatible systems of ladic sheaves on a smooth curve over a finite field are compatible along the boundary. I will present an extension of Deligne's theorem to schemes of finite type over the ring of integers of a local field. This has applications to the equicharacteristic case of some conjectures on lindependence. I will also discuss the relationship with compatible wild ramification. This is joint work with Qing Lu. 
Mon Mar 11 
Representations of padic groups7:30pm  Vincent Hall 213Representations of padic groups 
Mon Mar 11 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Mon Mar 11 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Applied and Computational Mathematics Seminar 
Mon Mar 11 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium Canceled 
Mon Mar 11 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Mar 11 
IMA Data Science Lab Seminar1:25pm  Lind 305Robust and Phaseless PCA (and Subspace Tracking) Namrata Vaswani, Iowa State University Abstract:Principal Components Analysis (PCA), a.k.a. subspace learning, is one of the most widely used dimension reduction techniques that attempts to find a lowdimensional subspace approximation of a given dataset. PCA is a solved problem when the observed data is relatively clean and lies in (or close to) a lowdimensional subspace. However, in many modern applications, the data are often either incomplete (missing data) or corrupted by outliers. Robust PCA refers to this harder problem of PCA in the presence of entrywise outliers (sparse corruptions). An important example application is video analytics when slowchanging videos are corrupted by foreground occlusions, e.g., by moving vehicles or persons. For long data sequences, e.g., long surveillance videos, if one tries to use a single subspace to represent the entire sequence, the required subspace dimension may be too large. For such data, a better model is to assume that the data subspace can change with time, albeit gradually. This problem of tracking data lying in a slowly changing subspace, while being robust to additive sparse outliers is referred to as Robust Subspace Tracking (RST). While robust PCA has received a lot of attention in the last decade, its dynamic version, RST, was largely open until recently. In a recent body of work, we have introduced the first provably correct and practically usable online solution framework for RST that we call Recursive Projected Compressive Sensing (ReProCS). Our most recent work from ICML 2018 shows that a simple ReProCSbased algorithm provides a provably fast and nearly (delay and memory) optimal RST solution under mild assumptions: weakened standard robust PCA assumptions and subspace change that is slow enough compared to the smallest magnitude outlier entry. Our theoretical claims are also backed by extensive experimental evidence for two video applications. In new work, we have looked at what can be called the ``Phaseless PCA problem. This involves recovering a lowrank matrix from phaseless (magnitudeonly) linear projections of each of its columns. It finds important applications in dynamic phaseless imaging applications, such as dynamic subdiffraction imaging or Fourier ptychography, involving recovering a set of slowlychanging images that together form an approximately lowrank matrix (with each vectorized image being one column). We introduce a simple alternating minimization solution that can provable recover the lowrank matrix with sa 
Fri Mar 08 
First Year Seminar6:30pm  Vincent 364First Year Seminar TBA 
Fri Mar 08 
MCFAM Seminar5:30pm  Vincent Hall 16Feb 2018 Volatility Event Yuepeng Perry Li, CFA, FRM, Parametric Portfolio Associates LLC Abstract:On the Monday of February 5th 2018, VIX Index (measure of expected future volatility) spiked by 116% to 37.3, and massive turbulence was observed across global financial markets. During the talk, we will review this event and discuss on the following topics:

Fri Mar 08 
Combinatorics Seminar3:35pm  Vincent Hall 570Affine matrixball construction and its relation to representation theory Dongkwan Kim, University of Minnesota Abstract:In 1985, Shi found a generalization of the RobinsonSchensted algorithm to (extended) affine symmetric groups and described their KazhdanLusztig cells in terms of combinatorics. Recently, Chmutov, Lewis, Pylyavskyy, and Yudovina developed its generalization, called the affine matrixball construction (abbreviated AMBC). It provides a bijection from an (extended) affine symm 