Past Seminars
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 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
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). 
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 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
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 
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 
PDE Seminar3:35pm  Vincent Hall 570PDE Seminar 
Wed Oct 02 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
Wed Oct 02 
Student Number Theory Seminar3:35pm  Vincent Hall 6Student Number Theory Seminar 
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 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 6Applied and Computational Mathematics Seminar 
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 
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 16Colloquium 
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 
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 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 213Automorphic Forms and Number Theory 
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. 
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 symmetric group to the set of triples (P,Q,?) where P and Q are rowstandard Young tableaux of the same shape and ? is an integer vector satisfying certain inequalities. In this talk, I will briefly explain this algorithm, and discuss how this is related to representation of (extended) affine symmetric groups, especially the asymptotic Hecke algebras introduced by Lusztig. This work is joint with Pavlo Pylyavskyy. 
Fri Mar 08 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Mar 08 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Mar 08 
1:25pm  Lind 305 Internship/Job Searching 101: Answering Your Most Asked Beginner Questions Whitney Moore, University of Minnesota, Twin Cities Abstract:Internship/job searching is a multifaceted process that can summon many questions along the way! During this workshop, we will aim to address your most asked questions about getting started with your search, including: Whitney Moore has been a Career Counselor in the CSE Career Center at the University of Minnesota since the fall of 2011. Her passion lies in living a life of positivity and inspiring others to do the same, particularly while navigating career and leadership development. In addition to her work at the U of M, Whitney is a past President of the Minnesota College and University Career Services Association (MCUCSA) and holds degrees from Gustavus Adolphus College and Minnesota State University, Mankato. Away from campus, Whitney is motivated by running with her dog, competing in triathlon, eating baked goods, and exploring MN with her husband. As an utter positivist, you can also find her musings on living with positivity on Instagram at @ThePositivistExplorer! 
Fri Mar 08 
Probability Seminar8:30am CANCELLED 
Thu Mar 07 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Mar 07 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Mar 07 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Commutative Algebra Seminar 
Thu Mar 07 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Mar 07 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Thu Mar 07 
Student Number Theory Seminar11:00am  Vincent Hall 213Knots and Primes Eric Stucky, University of Minnesota Abstract:In this talk we will outline the basic premise for the analogy between knots (in manifolds) and primes (in number fields). This analogy involves some rather heavy definitions; we will review the topological background as needed, while taking a more intuitive angle on the arithmetic machinery. Time permitting, we will briefly sketch an extension of the Frobenius automorphism which is a major tool in understanding the analogy between the Legendre symbol and the linking number. 
Thu Mar 07 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Mar 06 
Representations of padic groups8:30pm  Vincent Hall 213Representations of padic groups 
Wed Mar 06 
AMS Intro to Research Seminar6:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed Mar 06 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Generic Jordan forms and plane partitions Sam Hopkins, University of Minnesota Abstract:We continue the introduction of the GarverPatriasThomas paper by 
Wed Mar 06 
PDE Seminar3:35pm  Vincent Hall 570Quantitative estimates of propagation of chaos for large systems of interacting particles Zhenfu Wang, University of Pennsylvania Abstract:We present a new method to derive quantitative estimates proving the propagation of chaos for large stochastic or deterministic systems of interacting particles. Our approach requires to prove large deviations estimates for noncontinuous potentials modified by the limiting law. But it leads to explicit bounds on the relative entropy between the joint law of the particles and the tensorized law at the limit; and it can be applied to very singular kernels that are only in negative Sobolev spaces and include the BiotSavart law for 2D NavierStokes and 2D Euler. Joint work with P.E. Jabin. 
Tue Mar 05 
Colloquium3:35pm  Vincent Hall 16Cohomology of Shimura varieties Sug Woo Shin, U.C. Berkeley Abstract:Shimura varieties are a certain class of algebraic varieties over number fields with lots of symmetries, introduced by Shimura and Deligne nearly half a century ago. They have been playing a central role in number theory and other areas. Langlands proposed a program to compute the Lfunctions and cohomology of Shimura varieites in 1970s; this was refined by LanglandsRapoport and Kottwitz in 1980s. I will review some old and recent results in this direction. 
Tue Mar 05 
Dynamical Systems2:30pm  Vincent Hall 313Measuring attractor strength using bounded, nonautonomous control Kate Meyer, UMN Abstract:A topological definition of an attractor leaves out metric information relevant to modeling realworld systems, particularly how far the attractor persists against perturbations and error. This talk will review some existing approaches to measuring the strength of an attractor in metric terms and will introduce the quantity intensity to generalize basin steepness to systems of autonomous ODEs in arbitrary dimension. One can compute an attractors intensity by probing a domain of attraction with bounded, nonautonomous control and tracking the sets reachable from the attractor. A connection between reachable sets and isolating blocks implies that an attractors intensity not only reflects its capacity to retain solutions under timevarying perturbations, but also gives a lower bound on the distance the attractor continues in the space of vector fields. 
Tue Mar 05 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Mar 05 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Mon Mar 04 
Representations of padic groups8:30pm  Vincent Hall 213Representations of padic groups 
Mon Mar 04 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory 
Mon Mar 04 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Applied and Computational Mathematics Seminar 
Mon Mar 04 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon Mar 04 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Mar 04 
IMA Data Science Lab Seminar1:25pm  Lind 305Peculiar Properties of Locally Linear Embedding  Toward Theoretical Understanding of Unsupervised Learning Hautieng Wu, Duke University Abstract:Since its introduction in 2000, the locally linear embedding (LLE) has been widely applied as an unsupervised learning tool. However, only few handwaiving arguments are available to explain what is going on before 2018. For the sake of scientific soundness, we provide a systematic analysis of LLE, particularly under the manifold setup. In this talk, several theoretical results will be discussed. (1) We derive the corresponding kernel function, which in general is asymmetric and and not form a Markov process. (2) The regularization is critical. Different regularizations lead to dramatically different results. If chosen correctly, asymptotically we obtain the LaplaceBeltrami operator even under nonuniform sampling. (3) It has an intimate relationship with the local covariance analysis and tangent bundle structure. (4) When the boundary is not empty, we run into an interesting mixedtype differential equation. (5) An ingredient of the kernel provides a novel way to detect boundary, and hence a new approach to derive the LaplaceBeltrami operator with the Dirichlet boundary condition. If time permits, its relationship with several statistical topics like the locally linear regression and error in variable will be discussed. This is a joint work with Nan Wu. 
Fri Mar 01 
First Year Seminar6:30pm  Vincent 364First Year Seminar TBA 
Fri Mar 01 
MCFAM Seminar5:30pm  Vincent Hall 16Introduction to model selection principles for data analysis in the era of Big Data Jie Ding, School of Statistics  University of Minnesota Abstract:In the era of big data, analysts usually explore various statistical models or machine learning methods for observed data in order to facilitate scientific discoveries or gain predictive power. Whatever data and fitting procedures are employed, a crucial step is to select the most appropriate model or method from a set of candidates. Model selection is a key ingredient in data analysis for reliable and reproducible statistical inference or prediction, and thus central to scientific studies in fields such as ecology, economics, engineering, finance, political science, biology, and epidemiology. There has been a long history of model selection techniques that arise from researches in statistics, information theory, and signal processing. A considerable number of methods have been proposed, following different philosophies and exhibiting varying performances. The purpose of this talk is to bring an overview of them, in terms of their motivation, large sample performance, and applicability. I will provide practically relevant discussions on theoretical properties of stateof theart model selection approaches, and share some thoughts on controversial views on the practice of model selection. Bio for Jie Ding: https://cla.umn.edu/statistics/newsevents/story/newfacultymemberchar... 
Fri Mar 01 
Combinatorics Seminar3:35pm  Vincent Hall 570Quotients of symmetric polynomial rings deforming the cohomology of the Grassmannian Darij Grinberg Abstract:One of the many connections between Grassmannians and combinatorics is cohomological: The cohomology ring of a Grassmannian Gr(k,n) is a quotient of the ring S of symmetric polynomials in k variables. More precisely, it is the quotient of S by the ideal generated by the k consecutive complete homogeneous symmetric polynomials hn?k+1,hn?k+2,...,hn. We propose and begin to study a deformation of this quotient, in which the ideal is instead generated by hn?k+1?a1,hn?k+2?a2,...,hn?ak for some k fixed elements a1,a2,...,ak of the base ring. This generalizes both the classical and the quantum cohomology rings of Gr(k,n). We find two bases for the new quotient, as well as an S3symmetry of its structure constants, a "rim hook rule" for straightening arbitrary Schur polynomials, and a fairly complicated Pieri rule. We conjecture that the structure constants are nonnegative in an appropriate sense (treating the ai as signed indeterminate), which suggests a geometric or combinatorial meaning for the quotient. There are multiple open questions and opportunities for further research. 
Fri Mar 01 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Mar 01 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Mar 01 
1:25pm  Lind 305 Lecture Sohan Das, EVS, Inc. 
Fri Mar 01 
Probability Seminar8:30am CANCELLED 
Thu Feb 28 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Feb 28 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Feb 28 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Virtual Resolutions of Monomial Ideals Jay Yang, University of Minnesota Abstract:Virtual resolutions as defined by Berkesch, Erman, and Smith, 
Thu Feb 28 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Feb 28 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Thu Feb 28 
Student Number Theory Seminar11:00am  Vincent Hall 213Finite Hecke Algebras and Their Characters Andy Hardt, University of Minnesota Abstract:We explore some of the major results in the study of finite Hecke algebras and their character tables. These algebras are useful in the study of representations of finite Chevalley groups, and also appear in the study of quantum groups and knot/link invariants. We'll run through some equivalent definitions of this versatile object, and then talk about a couple approaches to its character theory. In particular, Starkey's rule is a combinatorial formula for the character table of the type A finite Hecke algebra. We'll briefly sketch a proof of this result and talk about the possibility for extension to other types. Starkey's rule allows us to calculate the weights of Ocneanu traces, which are important invariants in knot theory relating to type A Hecke algebras, and a type B version of Starkey's rule would give us insights into the type B analogue to Ocneanu traces. 
Thu Feb 28 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Feb 27 
Representations of padic groups8:30pm  Vincent Hall 213Representations of padic groups 
Wed Feb 27 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Jordan form data of quiver representations Sam Hopkins, University of Minnesota Abstract:We introduce the paper of Garver, Patrias and Thomas: Minuscule reverse plane partitions via quiver representations, starting with a review of aspects of quiver representations. 
Wed Feb 27 
AMS Intro to Research Seminar12:20pm  Vincent Hall 570AMS Intro to Research Seminar Adrienne Sands 
Tue Feb 26 
Dynamical Systems2:30pm  Vincent Hall 313Spectral Consequences of Hidden Symmetry in Network Dynamical Systems Eddie Nijholt, UIUC Abstract:Network dynamical systems play an important role in many fields of science; whenever there are agents whose time evolution is linked through some interaction structure, we may view the system as a network and model it accordingly. However, despite their prevalence, network dynamical systems are in general not well understood. One can identify two reasons for this. First of all, many coordinate changes and other transformations from wellknown dynamical systems techniques do not respect the underlying network structure. Second of all, despite this somewhat `ethereal' character, systems with a network structure often display behavior that is highly anomalous for general dynamical systems. Examples of this include very unusual bifurcation scenarios and high spectral degeneracies. As a possible explanation of this, it can be shown that a large class of network ODEs admit hidden symmetry, which may be discovered through the socalled fundamental network construction. In most cases, this underlying symmetry does not come from a group though, but rather from a more general algebraic structure such as a monoid or category. I will show how the fundamental network allows one to adapt techniques from dynamical systems theory to a network setting, and how some of the more unusual properties of networks may be explained. In doing so, I will mostly focus on spectral properties of linear network maps. 
Tue Feb 26 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Feb 26 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Mon Feb 25 
Representations of padic groups8:30pm  Vincent Hall 213Representations of padic groups 
Mon Feb 25 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Integral representations and meromorphic continuations of Eisenstein series and Lfunctions Paul Garrett, University of Minnesota 
Mon Feb 25 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Primal dual methods for Wasserstein gradient flows Li Wang, University of Minnesota Abstract:We develop a variational method for nonlinear equations with a gradient flow structure. Such equations arise in applications of a wide range, such as porous median flows, material science, animal swarms, and chemotaxis. Our method builds on the JKO framework, which evolves the equation as a gradient flow with respect to the Wasserstein metric. As a result, our method has builtin positivity preserving, entropy decreasing properties, and overcomes stability issue due to the strong nonlinearity and degeneracy. Furthermore, our method is massively parallelizable, and thus extremely efficient in high dimensions. Upon discretization of the PDE constraint, we also prove the ??convergence of the fully discrete optimization towards the continuum JKO scheme. 
Mon Feb 25 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon Feb 25 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Feb 25 
IMA Data Science Lab Seminar1:25pm  Lind 305Strong Coresets for kMedian and Subspace Approximation: Goodbye Dimension David Woodruff, Carnegie Mellon University Abstract:We obtain the first strong coresets for the kmedian and subspace approximation problems with sum of distances objective function, on n points in d dimensions, with a number of weighted points that is independent of both n and d; namely our coresets have size poly(k/eps). A strong coreset (1+eps)approximates the cost function for all possible sets of centers simultaneously. We also give input sparsity time algorithms for computing these coresets, which are fixed parameter tractable in k/eps. We obtain the result by introducing a new dimensionality reduction technique for coresets that significantly generalizes earlier results for squared Euclidean distances to sums of pth powers of Euclidean distances for constant p >= 1. Joint work with Christian Sohler 
Fri Feb 22 
First Year Seminar6:30pm  Vincent 364First Year Seminar TBA 
Fri Feb 22 
MCFAM Seminar5:30pm  Vincent Hall 112The Prospect of a Forgivable Premium Insurance Policy Kyle Jore, University of Minnesota Abstract:Despite low premiums and high subsidies, farmers view crop insurance programs as a gamble. One explanation, in a revenue protection program, is that farmers exhibit loss aversion when premiums are just above coverage. Introducing a model for conditional loss aversion (CLA), in the context of cumulative prospect theory, it can be shown that the introduction of a forgivable premium can remove the producers loss aversion. This would result in producers being willing to spend more on an insurance program and thus, allow for a reduction in the implied subsidy. 
Fri Feb 22 
Combinatorics Seminar3:35pm  Vincent Hall 570Counting factorizations in complex reflection groups Joel Lewis, George Washington University Abstract:In this talk, I'll discuss ongoing work with Alejandro Morales generalizing a 30year old result of Jackson on permutation enumeration: we consider the enumeration of arbitrary factorizations of a Coxeter element in a well generated finite complex reflection group, keeping track of the fixed space dimension of the factors. As in the case of the symmetric group, the factorization counts are ugly, so the goal is to choose a basis for the generating function in which the answer is nice. In the case of the infinite families of monomial matrices, we accomplish this via combinatorial arguments; a notion of transitivity of a factorization appears for the "type D" group G(m, m, n). I'll also describe some puzzling partial results in the exceptional cases. 
Fri Feb 22 
PDE Seminar3:35pm  Vincent Hall 311Special PDE Seminar  How to obtain parabolic theorems from their elliptic counterparts Blair Davey, City College of New York Abstract:Experts have long realized the parallels between elliptic and parabolic theory of partial differential equations. It is wellknown that elliptic theory may be considered a static, or steadystate, version of parabolic theory. And in particular, if a parabolic estimate holds, then by eliminating the time parameter, one immediately arrives at the underlying elliptic statement. Producing a parabolic statement from an elliptic statement is not as straightforward. In this talk, we demonstrate a method for producing parabolic theorems from their elliptic analogs. Specifically, we show that an $L^2$ Carleman estimate for the heat operator may be obtained by taking a highdimensional limit of $L^2$ Carleman estimates for the Laplacian. Other applications of this technique will be discussed. 
Fri Feb 22 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Feb 22 
Probability Seminar2:30pm  Vincent Hall 213Largest Entries of Sample Correlation Matrices from Equicorrelated Normal Populations Tiefeng Jiang, UMN Abstract:We the limiting distribution of the largest offdiagonal entry of the sample correlation matrices of highdimensional Gaussian populations with equicorrelation structure. Assume the entries of the population distribution have a common correlation coefficient r >0 and both the population dimension p and the sample size n tend to infinity with log p=o(n^{1/3}). 
Fri Feb 22 
1:25pm  Lind 305 Industrial Problems in Digital Retail Samantha Schumacher, Target Corporation Abstract:Target is rapidly growing into the online retail space. Behind that growth, there are a lot of advanced mathematical problems to solve. Some mathematics problems in supply chain are easy to spot (traveling salesman problem!), and some are less obvious. Well talk through at least 2 lessobvious problems which are currently being investigated by Targets Supply Chain analytics teams. The goal of this talk is to give insight into the broad range of problems we are solving at Target. Additionally, Ill spend a little time talking about solutions. What makes a good solution in Industry? What makes a good problem? Samantha Schumacher has been working math problems at Target for the last 5 years. She currently leads an analytics and engineering team for the network planning & digital fulfillment of Targets supply chain. She has her PhD in applied mathematics from University of Minnesota and an undergraduate degree in theater from Smith College. So, if all goes according to plan, she will use those theater skills to keep the talk engaging! She is also the longtime author of the blog: www.SocialMathematics.net which considers the interaction of mathematics and the modern world. 
Fri Feb 22 
Probability Seminar8:30am CANCELLED 
Thu Feb 21 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Feb 21 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Feb 21 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Commutative Algebra Seminar 
Thu Feb 21 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Feb 21 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Thu Feb 21 
Student Number Theory Seminar11:00am  Vincent Hall 213Student Number Theory Seminar  Cancelled 
Thu Feb 21 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Feb 20 
Representations of padic groups8:30pm  Vincent Hall 213Representations of padic groups TBD 
Wed Feb 20 
AMS Intro to Research Seminar6:20pm  Vincent Hall 570AMS Intro to Research Seminar 
Wed Feb 20 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Semisimplicity of Deligne's category Rep(S_t) Peter Webb, University of Minnesota Abstract:Continuing to follow the paper of Comes and Ostrik, On blocks of Deligne's category Rep(S_t), we prove the result in Section 3 that the category is semisimple except for countably. many values of t. The proof is an interesting use of the characterization of semisimple algebras by nondegeneracy of the trace form. 
Tue Feb 19 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Feb 19 
Math Physics Seminar12:20pm  Vincent Hall 209Invariants of Finite and Discrete Group Actions Via Moving Frames Peter Olver Abstract:The equivariant moving frame method is adapted to algorithmically construct complete, minimal sets of generating invariants for finite or, more generally, discrete group actions, both linear and nonlinear. The resulting invariants are piecewise analytic and admit a rewrite rule that allows one to immediately express any other invariant (polynomial, rational, smooth, analytic, etc.) as a function of the generating invariants. The talk will be elementary and no a priori knowledge of invariant theory or moving frames will be assumed. 
Tue Feb 19 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Mon Feb 18 
Representations of padic groups8:30pm  Vincent Hall 213Representations of padic groups 
Mon Feb 18 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Integral Representations Paul Garrett, University of Minnesota 
Mon Feb 18 
Applied and Computational Mathematics Seminar3:35pm  Vincent Hall 113Nonperturbative nonlinear effects in the dispersion relations for TE and TM plasmons on twodimensional materials Vera Andreeva Abstract:We analytically obtain the dispersion relations for transverseelectric (TE) and transversemagnetic (TM) surface plasmonpolaritons in a nonlinear twodimensional (2D) conducting material with inversion symmetry lying between two Kerrtype dielectric media. To this end, we use Maxwell's equations within the quasielectrostatic, weakly dissipative regime. We show that the wavelength and propagation distance of surface plasmons decrease due to the nonlinearity of the surrounding dielectric. In contrast, the effect of the nonlinearity of the 2D material depends on the signs of the real and imaginary parts of the thirdorder conductivity. Notably, the dispersion relations obtained by naively replacing the permittivity of the dielectric medium by its nonlinear counterpart in the respective dispersion relations of the linear regime are not accurate. We apply our analysis to the case of doped graphene and make predictions for the surface plasmon wavelength and propagation distance. 
Mon Feb 18 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 313Applied and Computational Math Colloquium 
Mon Feb 18 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Feb 15 
First Year Seminar6:30pm  Vincent 364First Year Seminar TBA 
Fri Feb 15 
MCFAM Seminar5:30pm  Vincent Hall 16Simulating the Greeks of American Options P.A. (Phuong Anh) Nguyen, University of Minnesota Abstract:Abstract: In this paper, we implement an efficient simulationbased method for estimating the Greeks of American options. We perform a least square regression to determine the optimal stopping rule that is applied to calculate the Greeks, which are derived via a pathwise derivative approach. We prove that this method provides asymptotically unbiased simulation estimators for the Greeks. In addition, we propose a boundary integral technique as a faster way to approximate gamma. This technique can also be used to calculate delta and theta. Our paper is the first to provide complete simulationbased approximations for all of the Greeks (delta, gamma, theta, rho, and vega) of American options. To make the computational process more efficient, we incorporate a Brownian Bridge into the numerical simulations. We then extend the application to American basket options. Bio: P.A. Nguyen is a PhD candidate in the University of Minnesota's Industrial Systems Engineering (ISyE) Doctoral Program. She is working with Dr. Dan Mitchell whose focus is in the area of financial engineering, specifically applying stochastic control to problems in finance and quantitative risk management. P.A. is also an alumna of the Master of Financial Mathematics (MFM) at the University of Minnesota (2014) and is currently a teaching assistant for the MFM. She worked in enterprise risk management, primarily in credit risk and interest rate risk areas, for a few years before joining UMNs ISyE PhD program. 
Fri Feb 15 
Lie Theory Seminar3:35pm  Vincent Hall 313Lie Theory Seminar Lue Pan,, University of Chicago 
Fri Feb 15 
Special Events and Seminars3:35pm  Vincent Hall 313FontaineMazur conjecture in the residually reducible case (II) Lue Pan, University of Chicago Abstract:We prove the modularity of some twodimensional residually reducible padic Galois representations over Q when p is at least 5. In the first talk, I will present a generalization of Emerton's localglobal compatibility result. In the second talk, I will use this compatibility result to make a patching argument for completed homology in this setting. 
Fri Feb 15 
Combinatorics Seminar3:35pm  Vincent Hall 570Plabic RMatrices Sunita Chepuri, University of Minnesoa Abstract:Postnikov's plabic graphs in a disk are used to parametrize totally positive Grassmannians. One of the key features of this theory is that if a plabic graph is reduced, the face weights can be uniquely recovered from boundary measurements. On surfaces more complicated than a disk this property is lost. In this talk, we investigate a certain semilocal transformation of weights for plabic networks on a cylinder that preserves boundary measurements. We call this a plabic Rmatrix. We explore the properties of the plabic Rmatrix, including the symmetric group action it induces on plabic networks and its underlying cluster algebra structure. 
Fri Feb 15 
Probability Seminar2:30pm  Vincent Hall 213Probability Seminar 
Fri Feb 15 
Probability Seminar8:30am CANCELLED 
Thu Feb 14 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Feb 14 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Feb 14 
Special Events and Seminars1:25pm  Vincent Hall 113FontaineMazur conjecture in the residually reducible case (I) Lue Pan, University of Chicago Abstract:We prove the modularity of some twodimensional residually reducible padic Galois representations over Q when p is at least 5. In the first talk, I will present a generalization of Emerton's localglobal compatibility result. In the second talk, I will use this compatibility result to make a patching argument for completed homology in this setting. 
Thu Feb 14 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Commutative Algebra Seminar 
Thu Feb 14 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Feb 14 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Thu Feb 14 
Student Number Theory Seminar11:00am  Vincent Hall 213Counting Number Fields, Second Order Asymptotics, and Hurwitz Spaces Greg Michel, University of Minnesota Abstract:I'll introduce wellknown counting conjectures related to number fields of bounded discriminants, and then I'll talk about some semirelated topological ideas that may allow us to strengthen these conjectures in certain situations. 
Thu Feb 14 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Feb 13 
Representations of padic groups8:30pm  Vincent Hall 213Representations of padic groups TBD 
Wed Feb 13 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Indecomposable objects in Deligne's category Rep(S_t)  continuation Peter Webb, University of Minnesota Abstract:We continue with Section 3 of the paper by Comes and Ostrik, On blocks of Deligne's category Rep(S_t). Section 3 begins with the result that the indecomposable objects are parametrized by partitions of all sizes, and this has to do with a description of the idempotents in the partition algebras. We use a fundamental relationship that goes back to Green, between idempotents an algebra, and idempotents in a factor algebra by an idempotent, and in the algebra obtained by cutting by that idempotent. 
Wed Feb 13 
AMS Intro to Research Seminar12:20pm  Vincent Hall 5701st Annual AMS Sock Derangement TBA Abstract:In combinatorics there is a classic problem about a "hat check," where patrons submit their hats, return slips are lost, and people get them back willy nilly. People get sad, angry, happy, you name it! In fact, as the number of people checking hats goes to infinity, the probability that NO ONE gets their hat back goes to 1/e! Well, here at the U of M math department, we are all about generalizations. Therefore, we present to you: The 1st annual AMS Sock Derangement! (a generalization of the AMS hat check) 
Tue Feb 12 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Feb 12 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Feb 12 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Tue Feb 12 
PDE Seminar10:00am  Vincent Hall 570Global existence in incompressible fluid equations Javier GomezSerrano, Princeton University Abstract:There has been high scientific interest to understand the behavior of the surface quasigeostrophic (SQG) equation because it is a possible model to explain the formation of fronts of hot and cold air and because it also exhibits analogies with the 3D incompressible Euler equations. It is not known at this moment if this equation can produce singularities or if solutions exist globally. In this talk, I will discuss some recent works on the existence of global solutions for the SQG and modified SQG equations. 
Mon Feb 11 
MCFAM Distinguished Lecture Series5:30pm  Vincent Hall 16Coding Capital: The Legal vs. The Digital Code Katharina Pistor, Columbia Law School Abstract:In my forthcoming book, The Code of Capital: How Law Creates Wealth and Inequality, I argue that capital is coded in law, or more specifically in core institutions of private law, including property, collateral, trust, corporate, bankruptcy as well as contract law. These modules of the code of capital bestow critical attributes on simple assets, such as objects or claims, and there by transform them from simple into a wealth generating assets. These attributes are priority, durability, convertibility and universality, and critically, they depend on effective state backing. Recently, law has met a potential competitor in the form of the digital code. Blockchain and similar technologies, in particular, makes it possible to encode commitments such that they will be executed irrespective of a change of heart, or circumstances. Decentralized verification of resources and rights instead of ex post vindication of legal title promises a world without courts and without coercive law enforcement. In short, a new code may be on the horizon and its relation to the legacy, or legal, code raises fundamental questions about how to organize economic relations in an uncertain world and about who gets to set the parameters for doing so. Bio: Katharina Pistor is the Edwin B. Parker Professor of Comparative Law at Columbia Law School and director of the Law Schools Center on Global Legal Transformation. Her research and teaching spans corporate law, corporate governance, money and finance, property rights, comparative law and law and development. She has published widely in legal and interdisciplinary journals and is the author can coauthor of several books. She is the recipient of the Max Planck Research Award (2012) and of several grants by, among others the Institute for New Economic Thinking, and the National Science Foundation. Her most recent book, The Code of Capital: How the Law Creates Wealth and Inequality is forthcoming at Princeton University Press. 
Mon Feb 11 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Integral representations of cuspidaldata Eisenstein series Paul Garrett, University of Minnesota 
Mon Feb 11 
PDE Seminar3:35pm  Vincent Hall 313ComputerAssisted Proofs in Partial Differential Equations Javier GomezSerrano, Princeton University Abstract:In the last 50 years computing power has experienced an enormous development: every two years the number of transistors has doubled since the 1970s. However, even nowadays when we can perform very fast computations it is not clear a priori if one can obtain rigorous results based on the output of computer calculations. In this talk I will explain the basics of interval analysis and how it can be used to prove theorems in different contexts of PDE, ranging from fluid dynamics to spectral geometry. 
Mon Feb 11 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Feb 11 
Applied and Computational Mathematics Seminar3:30pm  Vincent Hall 113Applied and Computational Mathematics Seminar Vera Andreeva rescheduled  February 18 
Mon Feb 11 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Greg Shakhnarovich, Toyota Technological Institute at Chicago 
Fri Feb 08 
First Year Seminar6:30pm  Vincent 364First Year Seminar TBA 
Fri Feb 08 
MCFAM Seminar5:30pm  Vincent Hall 16Today's Seminar  Canceled Jie Ding, School of Statistics  University of Minnesota Abstract:In the era of big data, analysts usually explore various statistical models or machine learning methods for observed data in order to facilitate scientific discoveries or gain predictive power. Whatever data and fitting procedures are employed, a crucial step is to select the most appropriate model or method from a set of candidates. Model selection is a key ingredient in data analysis for reliable and reproducible statistical inference or prediction, and thus central to scientific studies in fields such as ecology, economics, engineering, finance, political science, biology, and epidemiology. There has been a long history of model selection techniques that arise from researches in statistics, information theory, and signal processing. A considerable number of methods have been proposed, following different philosophies and exhibiting varying performances. The purpose of this talk is to bring an overview of them, in terms of their motivation, large sample performance, and applicability. I will provide practically relevant discussions on theoretical properties of stateof theart model selection approaches, and share some thoughts on controversial views on the practice of model selection. Bio for Jie Ding 
Fri Feb 08 
Combinatorics Seminar3:35pm  Vincent Hall 570Whitney Numbers for Cones Galen DorpalenBarry, University of Minnesota Abstract:An arrangement of hyperplanes dissects space into connected components called chambers. A nonempty intersection of halfspaces from the arrangement will be called a cone. The number of chambers of the arrangement lying within the cone is counted by a theorem of Zaslavsky, as a sum of certain nonnegative integers that we will call the cone's "Whitney numbers of the 1st kind". For cones inside the reflection arrangement of type A (the braid arrangement), cones correspond to posets, chambers in the cone correspond to linear extensions of the poset, and these Whitney numbers refine the number of linear extensions. We present some basic facts about these Whitney numbers, and interpret them for two families of poset 
Fri Feb 08 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Feb 08 
Probability Seminar2:30pm  Vincent Hall 213Stability of the BakryEmery theorem on R^n Tom Courtade, UC Berkeley Abstract:In R^n, the BakryÉmery theorem states that the sharp constant in various functional inequalities for uniformly logconcave measures is no worse than the sharp constant for the Gaussian measure. As a consequence, uniformly logconcave measures inherit certain nice features of the Gaussian, like good measure concentration properties. In this talk, I'll discuss quantitative stability estimates for the BakryÉmery bound on logarithmic Sobolev and Poincaré constants. In particular, if a 1uniformly logconcave measure has almost the same logarithmic Sobolev or Poincaré constant as the standard Gaussian measure, then it must (almost) split off a Gaussian factor. As a corollary, we obtain dimensionfree stability estimates for Gaussian concentration of Lipschitz functions. The proofs combine Steins method, optimal transport, and simple variational arguments. Joint work with Max Fathi. 
Fri Feb 08 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Lecture Karyn Sutton, The Institute for Disease Modeling 
Fri Feb 08 
Probability Seminar8:30am CANCELLED 
Thu Feb 07 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Feb 07 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Feb 07 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Commutative Algebra Seminar 
Thu Feb 07 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Feb 07 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Thu Feb 07 
Student Number Theory Seminar11:00am  Vincent Hall 213Student Number Theory Seminar 
Thu Feb 07 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Feb 06 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Indecomposable objects in Deligne's category Rep(S_t) Peter Webb, University of Minnesota Abstract:We will start on Section 3 of the paper by Comes and Ostrik, On blocks of Deligne's category Rep(S_t). This will be preceded by a review of the setup in this category, which is built up out of partition algebras. Section 3 begins with the result that the indecomposable objects are parametrized by partitions of all sizes. 
Tue Feb 05 
Colloquium3:35pm  Vincent Hall 16A Multiscale/Multiphysics Coupling Framework for Heart Valve Damage Yue Yu, Lehigh University Abstract:Bioprosthetic heart valves (BHVs) are the most popular artificial replacements for diseased valves that mimic the structure of native valves. However, the life span of BHVs remains limited to 1015 years, and the mechanisms that underlie BHVs failure remain poorly understood. Therefore, developing a unifying mathematical framework which captures material damage phenomena in the fluidstructure interaction environment would be extremely valuable for studying BHVs failure. Specifically, in this framework the computational domain is composed of three subregions: the fluid (blood) , the fracture structure (damaged BHVs) modeled by the recently developed nonlocal (peridynamics) theory, and the undamaged thin structure (undamaged BHVs). These three subregions are numerically coupled to each other with proper interface boundary conditions. In this talk, I will introduce two subproblems and the corresponding numerical methods we have developed for this multiscale/multiphysics framework. In the first problem the coupling strategy for fluid and thin structure is investigated. This problem presents unique challenge due to the large deformation of BHV leaflets, which causes dramatic changes in the fluid subdomain geometry and difficulties on the traditional conforming coupling methods. To overcome the challenge, the immersogeometric method was developed where the fluid and thin structure are discretized separately and coupled through penalty forces. To ensure the capability of the developed method in modeling BHVs, we have verified and validated this method. The second problem focuses on the nonlocal Neumanntype interface boundary condition which plays a critical role in the fluidperidynamics coupling framework. In the nonlocal models the Neumanntype boundary conditions should be defined in a nonlocal way, namely, on a region with nonzero volume outside the surface, while in fluidstructure interfaces the hydrodynamic loadings from the fluid side are typically provided on a sharp codimensional one surface. To overcome this challenge, we have proposed a new nonlocal Neumanntype boundary condition which provides an approximation of physical boundary conditions on a sharp surface, with an optimal asymptotic convergence rate to the local counter part. Based on this new boundary condition, we have developed a fluidperidynamics coupling framework without overlapping regions. 
Tue Feb 05 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Feb 05 
Math Physics Seminar12:20pm  Vincent Hall 209Choreography in 3body Classical Mechanics Sasha Turbiner, ICNUNAM, Mexico Abstract:By definition the choreography (dancing curve) is the trajectory Does there exist (non)Newtonian gravity for which the dancing curve is known 
Tue Feb 05 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Mon Feb 04 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory Postponed 
Mon Feb 04 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Feb 04 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Tom Needham, The Ohio State University 
Fri Feb 01 
First Year Seminar6:30pm  Vincent 364First Year Seminar TBA 
Fri Feb 01 
MCFAM Seminar5:30pm  Vincent Hall 16Computational Issues in Making Math Models Operational in Insurance Scott Monitor, VP & Financial Engineer  MFM alumnus, FSA Abstract:Many insurance companies offer a wide array of investment guarantees, and some of these are complicated and have no clear analytical solution. In order to manage these contracts and along with increased scrutiny from regulatory bodies, companies are having to value these contracts more frequently and in a greater number of runs. We will demonstrate methodologies and computational approaches to be able to perform analysis on these contract that can be actionable and timely. 
Fri Feb 01 
Combinatorics Seminar3:35pm  Vincent Hall 570Enumerating Linear Systems on Graphs David Perkinson, Reed College Abstract:To play the dollar game on a graph, start by assigning to each vertex a number of dollars of either wealth or debt. From this initial state, called a "divisor", the vertices lend and borrow with their neighbors according to chipfiring rules in an attempt to reach a debtfree state. The set of all possible winning states is the "complete linear system" of the divisor. We are interested in determining its cardinality. In the figure below, each vertex represents one of the 201 winning positions resulting from giving ten dollars to one vertex of the cycle graph on five vertices. This is joint work with Sarah Brauner and Forrest Glebe. 
Fri Feb 01 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Feb 01 
Probability Seminar2:30pm  Vincent Hall 213Nonequilibrium particle systems in inhomogeneous space Leonid Petrov, University of Virginia Abstract:I will discuss stochastic interacting particle systems in the KardarParisiZhang universality class evolving in onedimensional inhomogeneous space. The inhomogeneity means that the speed of a particle depends on its location. I will focus on integrable cases, i.e., for which certain observables can be written in an exact form suitable for asymptotic analysis. Examples include a new continuousspace version of TASEP (totally asymmetric simple exclusion process), and the pushTASEP (=longrange TASEP). For integrable systems, limit shapes of particles density can be described in an explicit way. Asymptotics of fluctuations around infinite traffic jams, also available explicitly, bring phase transitions of a novel nature. 
Fri Feb 01 
Probability Seminar8:30am CANCELLED 
Thu Jan 31 
Colloquium3:35pm  Vincent Hall 16From infinite random matrices over finite fields to square ice Leonid Petrov, University of Virginia Abstract:Asymptotic representation theory of symmetric groups is a rich and beautiful subject with deep connections with probability, mathematical physics, and algebraic combinatorics. A oneparameter deformation of this theory related to infinite random matrices over a finite field leads to randomization of the classical RobinsonSchensted correspondence between words and Young tableaux. Exploring such randomizations we find unexpected applications to six vertex (square ice) type models and traffic systems on a 1dimensional lattice. 
Thu Jan 31 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Jan 31 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Jan 31 
Commutative Algebra Seminar1:25pm  Vincent Hall 301Commutative Algebra Seminar 
Thu Jan 31 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Jan 31 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Thu Jan 31 
Student Number Theory Seminar11:00am  Vincent Hall 213Student Number Theory Seminar 
Thu Jan 31 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Wed Jan 30 
Algebraic Representation Theory Seminar4:40pm  Vincent Hall 206Postponed to next week Peter Webb, University of Minnesota Abstract:We will start on Section 3 of the paper by Comes and Ostrik, On blocks of Deligne's category Rep(S_t). This will be preceded by a review of the setup in this category, which is built up out of partition algebras. Section 3 begins with the result that the indecomposable objects are parametrized by partitions of all sizes. 
Tue Jan 29 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Jan 29 
Math Physics Seminar12:20pm  Vincent Hall 209Higher order superintegrability, Painlevé transcendents and representations of polynomial algebras Ian Marqutte, University of Queensland Abstract:I will review results on classification of quantum superintegrable systems on twodimensional Euclidean space allowing separation of variables in Cartesian coordinates and possessing an extra integral of third or fourth order. The exotic quantum potential satisfy a nonlinear ODE and have been shown to exhibit the Painleve property. I will also present different constructions of higher order superintegrable Hamiltonians involving Painleve transcendents using four types of building blocks which consist of 1D Hamiltonians allowing operators of the type Abelian, Heisenberg, Conformal or Ladder. Their integrals generate finitely generated polynomial algebras and representations can be exploited to calculate the energy spectrum. I will point out that for certain cases associated with exceptional orthogonal polynomials, these algebraic structures do not allow to calculate the full spectrum and degeneracies. I will describe how other sets of integrals can be build and used to provide a complete solution. 
Tue Jan 29 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Mon Jan 28 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 207Automorphic Forms and Number Theory Postponed 
Mon Jan 28 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Jan 28 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Guanglin Xu, University of Minnesota, Twin Cities 
Fri Jan 25 
First Year Seminar6:30pm  Vincent 364First Year Seminar TBA, TBA 
Fri Jan 25 
MCFAM Seminar5:30pm  Vincent Hall 16No MCFAM Seminar 
Fri Jan 25 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Jan 25 
Probability Seminar2:30pm  Vincent Hall 213Large deviations for sparse random graphs Nicholas Cook, Stanford University Abstract:Let $G=G(N,p)$ be an Erd\H{o}sR\'enyi graph on $N$ vertices (where each pair is connected by an edge independently with probability $p$). We view $N$ as going to infinity, with $p$ possibly going to zero with $N$. What is the probability that $G$ contains twice as many triangles as we would expect? I will discuss recent progress on this ``infamous upper tail" problem, and more generally on tail estimates for counts of any fixed subgraph. These problems serve as a test bed for the emerging theory of \emph{nonlinear large deviations}, and also connect with issues in extending the theory of \emph{graph limits} to handle sparse graphs. In particular, I will discuss our approach to the upper tail problems via new versions of the classic regularity and counting lemmas from extremal combinatorics, specially tailored to the study of random graphs in the large deviations regime. This talk is based on joint work with Amir Dembo. 
Fri Jan 25 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Lecture Eric Lind, Metro Transit 
Fri Jan 25 
Probability Seminar8:30am CANCELLED 
Thu Jan 24 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Jan 24 
Algebraic Geometry1:25pm  Vincent Hall 113Algebraic Geometry Seminar 
Thu Jan 24 
Math Club Seminar12:20pm  Vincent Hall 570Math Club 
Thu Jan 24 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Thu Jan 24 
Student Number Theory Seminar11:00am  Vincent Hall 213Student Number Theory Seminar 
Thu Jan 24 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 570Reading Seminar on Automorphic Forms 
Tue Jan 22 
Dynamical Systems2:30pm  Vincent Hall 313Dynamical Systems Seminar 
Tue Jan 22 
Colloquium2:30pm  Vincent Hall 16Multiscale Problems in Cell Biology Chuan Xue, Ohio State University Abstract:Complex biological systems involve multiple space and time scales. To get an integrated understanding of these systems involves multiscale modeling, computation and analysis. In this talk, I will discuss two such examples in cell biology and illustrate how to use multiscale methods to explain experimental data. The first example is on chemotaxis of bacterial populations. I will present recent progress on embedding information of single cell dynamics into models of cell population dynamics. I will clarify the scope of validity of the wellknown PatlakKellerSegel chemotaxis equation and discuss alternative models when it breaks down. The second example is on the axonal cytoskeleton dynamics in health and disease. I will present a stochastic multiscale model that gave the first mechanistic explanation for the cytoskeleton segregation phenomena observed in many neurodegenerative diseases. 
Tue Jan 22 
Math Physics Seminar12:20pm  Vincent Hall 209Math Physics Seminar 
Tue Jan 22 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Mon Jan 21 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Jan 18 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Jan 18 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Jan 18 
Probability Seminar8:30am CANCELLED 
Thu Jan 17 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Jan 15 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Mon Jan 14 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Jan 11 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Jan 11 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Jan 11 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Algebraic Representation Theory 
Fri Jan 11 
Probability Seminar8:30am CANCELLED 
Thu Jan 10 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Jan 08 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Mon Jan 07 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Jan 04 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Jan 04 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Jan 04 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Jan 04 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Algebraic Representation Theory 
Fri Jan 04 
Probability Seminar8:30am CANCELLED 
Thu Jan 03 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Jan 01 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Mon Dec 31 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Dec 28 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Dec 28 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Dec 28 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Dec 28 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Algebraic Representation Theory 
Fri Dec 28 
Probability Seminar8:30am CANCELLED 
Thu Dec 27 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Dec 25 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Mon Dec 24 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Fri Dec 21 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Dec 21 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Dec 21 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Dec 21 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Algebraic Representation Theory 
Fri Dec 21 
MathCEP Seminar10:10am  Vincent Hall 364MathCEP Seminar 
Fri Dec 21 
Probability Seminar8:30am CANCELLED 
Thu Dec 20 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Dec 20 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Projective Geometry, Complex Hyperbolic Space, and Geometric Transitions Steve Trettel, UC Santa Barbara Abstract:The natural analog of Teichmuller theory for hyperbolic manifolds in dimension 3 or greater is trivialized by Mostow Rigidity, so mathematicians have worked to understand more general deformations. Two well studied examples, convex real projective structures and complex hyperbolic structures, have been investigated extensively and provide independently developed deformation theories. Here we will discuss a surprising connection between the these, and construct a one parameter family of geometries deforming complex hyperbolic space into a new geometry built out of real projective space and its dual. This connects the aforementioned deformation theories and provides geometric motivation for a representationtheoretic observation of Cooper, Long, and Thistlethwaite 
Thu Dec 20 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Dec 20 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Dec 20 
Student Number Theory Seminar12:20pm  Vincent Hall 313Student Number Theory TBA 
Thu Dec 20 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Dec 19 
PDE Seminar3:30pm  Vincent Hall 570PDE Seminar 
Tue Dec 18 
Dynamical Systems2:30pm  Ford Hall 130Dynamical Systems Seminar 
Tue Dec 18 
Math Physics Seminar12:20pm  Vincent Hall 313Math Physics Seminar 
Tue Dec 18 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Mon Dec 17 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Automorphic Forms and Number Theory 
Mon Dec 17 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Dec 17 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Dec 17 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Dec 17 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Dec 14 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Dec 14 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Dec 14 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Dec 14 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Dec 14 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Algebraic Representation Theory 
Fri Dec 14 
MathCEP Seminar10:10am  Vincent Hall 364MathCEP Seminar 
Fri Dec 14 
Probability Seminar8:30am CANCELLED 
Thu Dec 13 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Dec 13 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Dec 13 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Dec 13 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Dec 13 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Dec 13 
Student Number Theory Seminar12:20pm  Vincent Hall 313Galois Representations and the Modularity Theorem Andy Hardt, University of Minnesota Abstract:I will continue Katy's talk from last week, and talk about chapter 9 of Diamond and Shurman's "A First Course in Modular Forms." We'll define Galois representations corresponding to both elliptic curves and modular forms. Then we'll state the modularity theorem, which asserts that every elliptic curve corresponds to a modular form, and their Galois representations are equal. If we have time, we'll relate this back to the version of the theorem from last week, which equated points on an elliptic curve to Fourier coefficients of a modular form. The proof of the theorem, however, will be left as an exercise to the listener. 
Thu Dec 13 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Dec 12 
PDE Seminar3:35pm  Vincent Hall 570Scattering for the 3D GrossPitaevskii equation Zihua Guo, Monash University Abstract:We study the Cauchy problem for the 3D GrossPitaevskii equation. Global wellposedness in the natural energy space was proved by Gerard. 
Tue Dec 11 
Dynamical Systems2:30pm  Ford Hall 130Dynamical Systems Seminar 
Tue Dec 11 
Math Physics Seminar12:20pm  Vincent Hall 313Application of Invariant Signatures: Solving Jigsaw Puzzles Rob Thompson 
Tue Dec 11 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Dec 11 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Dec 10 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Automorphic Forms and Number Theory 
Mon Dec 10 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Dec 10 
Special Events and Seminars3:35pm  Vincent Hall 207Optimal transport on graphs with Applications Wuchen Li Abstract:In recent years, optimal transport has many applications in evolutionary dynamics, statistics, and machine learning. In this talk, we introduce dynamical optimal transport on finite graphs. We proposed to study the probability simplex as a Riemannian manifold with a Wasserstein metric. We call it a probability manifold. Various developments, especially the FokkerPlanck equation, will be introduced. The entropy production on graphs related to Shannon entropy will be established. Its connection with Fisher information and Yanos formula will be studied. Many examples, including Mean field games, geometry of graphs, statistical learning problems, will be presented. 
Mon Dec 10 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: The geometric average size of Selmer groups over function fields Aaron Landesman, Stanford Abstract:We use topological methods to investigate the average size of nSelmer groups of elliptic curves over F_q(t). 
Mon Dec 10 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Dec 10 
IMA Data Science Lab Seminar1:25pm  Lind 305Stratifying HighDimensional Data Based on Proximity to the Convex Hull Boundary Lori Ziegelmeier, Macalester College Abstract:The convex hull of a set of points,C, serves to expose extremal properties of C and can help identify elements in C of high interest. For many problems, particularly in the presence of noise, the true vertex set (and facets) may be difficult to determine. One solution is to expand the list of high interest candidates to points lying near the boundary of the convex hull. We propose a quadratic program for the purpose of stratifying points in a data cloud based on proximity to the boundary of the convex hull. For each data point, a quadratic program is solved to determine an associated weight vector. We show that the weight vector encodes geometric information concerning the points relationship to the boundary of the convex hull. The computation of the weight vectors can be carried out in parallel, and for a fixed number of points and fixed neighborhood size, the overall computational complexity of the algorithm grows linearly with dimension. As a consequence, meaningful computations can be completed on reasonably large, highdimensional data sets. Lori Ziegelmeier received an A.S. and A.A. from Colby Community College in 2005. She completed her B.S. in Mathematics and B.A. in Liberal Arts and History, M.S. in Mathematics, and Ph.D. in Mathematics all at Colorado State University in 2007, 2009, and 2013, respectively. Since completing her doctoral degree, she has been in the Department of Mathematics, Statistics, and Computer Science at Macalester College and is currently an Assistant Professor. Her research is in the area of geometric and topological data analysis. 
Mon Dec 10 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Dec 07 
MCFAM Seminar5:30pm  Vincent Hall 16Data Visualization in R Chen Zhang, Sr. Consultant, Analytics & Research at Travelers; Ph.D. in Statistics from UConn; UMN MFM Alumnus Abstract:Data visualization is often overlooked by people working with data and/or modeling but can in fact reveal very useful insight into problems at hand. R is an opensource programming language for statistical computing and graphics with increasing popularity among practitioners in data science and machine learning in recent years. The "ggplot2" package in R, in particular, provides very powerful, intuitive and versatile tools for data visualization. An overview of these tools will be presented in this talk accompanied by a live demo. 
Fri Dec 07 
Lie Theory Seminar3:35pm  Vincent Hall 313Finiteness of Frobenius traces of a de Rham local system Koji Shimizu, University of California, Berkeley Abstract:Every smooth projective variety over a number field yields a Galois representation via etale cohomology, and the Weil conjecture tells that its Frobenius traces are integers. Fontaine and Mazur conjectured that Galois representations satisfying a local condition (de Rham) arise from geometry and hence have a similar finiteness property. In this talk, I will focus on de Rham local systems on algebraic varieties and explain a finiteness of Frobenius traces follows from the FontaineMazur conjecture for Galois representations and the generalized Riemann Hypothesis 
Fri Dec 07 
Combinatorics Seminar3:35pm  Vincent Hall 570Catalan Functions and kSchur functions Anna Pun, Drexel University Abstract:LiChung Chen and Mark Haiman studied a family of symmetric functions called Catalan (symmetric) functions which are indexed by pairs consisting of a partition contained in the staircase (n1, ..., 1,0) (of which there are Catalan many) and a composition weight of length n. They include the Schur functions, the HallLittlewood polynomials and their parabolic generalizations. They can be defined by a Demazureoperator formula, and are equal to GLequivariant Euler characteristics of vector bundles on the flag variety by the BorelWeilBott theorem. We have discovered various properties of Catalan functions, providing a new insight on the existing theorems and conjectures inspired by Macdonald positivity conjecture. A key discovery in our work is an elegant set of ideals of roots that the associated Catalan functions are kSchur functions and proved that graded kSchur functions are Gequivariant Euler characteristics of vector bundles on the flag variety, settling a conjecture of ChenHaiman. We exposed a new shift invariance property of the graded kSchur functions and resolved the Schur positivity and kbranching conjectures by providing direct combinatorial formulas using strong marked tableaux. We conjectured that Catalan functions with a partition weight are kSchur positive which strengthens the Schur positivity of Catalan function conjecture by ChenHaiman and resolved the conjecture with positive combinatorial formulas in cases which capture and refine a variety of problems. This is joint work with Jonah Blasiak, Jennifer Morse and Daniel Summers. 
Fri Dec 07 
Topology Seminar3:30pm  301 Vincent HallTopology Seminar: Power operations in normed motivic spectra Tom Bachmann, MIT Abstract:In joint work with M. Hoyois, we established (the beginnings of) a theory of "normed motivic spectra". These are motivic spectra with some extra structure, enhancing the standard notion of a motivic E_ooring spectrum (this is similar to the notion of Gcommutative ring spectra in equivariant stable homotopy theory). It was clear from the beginning that the homotopy groups of such normed spectra afford interesting *power operations*. In ongoing joint work with E. Elmanto and J. Heller, we attempt to establish a theory of these operations and exploit them calculationally. I will report on this, and more specifically on our proof of a weak motivic analog of the following classical result of Würgler: any (homotopy) ring spectrum with 2=0 is generalized EilenbergMacLane. 
Fri Dec 07 
Probability Seminar2:30pm  Vincent Hall 209When particle systems meet PDEs LiCheng Tsai, Columbia University Abstract:Interacting particle systems are models that involve many randomly evolving agents (i.e., particles). These systems are widely used in describing realworld phenomena. In this talk we will walk through three paradigmatic facets of interacting particle systems, namely the law of large numbers, random fluctuations, and large deviations. Within each facet, I will explain how Partial Differential Equations (PDEs) play a role in understanding the systems. 
Fri Dec 07 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Dec 07 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206The definition of Deligne's category Rep(S_t)  continuation Cecily Santiago, University of Minnesota Abstract:We will complete the steps in the definition of Deligne's category described in section 2.2 of the paper, On blocks of Deligne's category Rep(S_t), by Comes and Ostrik. 
Fri Dec 07 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305When Seeing is not Believing: New Forensics Algorithms to Detect Image Manipulations Michael Albright, Honeywell Abstract:Modern image editing software has made it possible to alter images in ways that can dramatically change the image content, yet the images may appear authentic to humans. While there are countless beneficial applications of photo editing, image manipulations can also be used in harmful ways e.g., altered images may be published to cause reputational harm, sway public opinions, influence elections, etc. Furthermore, with the growing popularity of social media and online sharing platforms, it is increasingly easy for altered media to go viral. Whats more, recent breakthroughs in artificial intelligence (AI) are making it dramatically easier to produce altered images, and even altered videos, that appear photo realistic. Hence, there is growing interest in developing new forensic methods that can detect manipulations in images and video. In this talk, I will give an overview of my teams work on the DARPAfunded Media Forensics (MediFor) Project to develop novel machinelearning algorithms for automated detection and localization of media manipulations. Michael Albright is a senior data scientist in the Data Science and Video Analytics group in Honeywell Labs in Golden Valley, Minnesota. Since joining Honeywell in 2015, he has invented new technologies that solve challenging problems for internal Honeywell businesses and external customers. His work has involved applying machine learning, optimization, and other applied math and computer science techniques to a variety of problems in domains ranging from Internet of Things (IoT) systems to computer vision applications. Michael earned a Ph.D. in theoretical physics from the University of Minnesota in 2015 and has previous industry experience at Cray, Inc. 
Fri Dec 07 
MathCEP Seminar10:10am  Vincent Hall 364Experiments in STEM Education Michelle Driessen, University of Minnesota Abstract:The general chemistry program has been experimenting with several new pedagogies in order to improve student learning and successful outcomes. Ill begin with our placement system and new adaptive courseware/learning analytics project, and will discuss any other project as time allows. 1. ALEKS Placement/Learning Modules 
Fri Dec 07 
Probability Seminar8:30am CANCELLED 
Thu Dec 06 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Dec 06 
Colloquium3:35pm  Vincent Hall 16Number theory over function fields and geometry Will Sawin, Columbia University Abstract:The function field model involves taking problems in 
Thu Dec 06 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Enumerative geometry: old and new Felix Janda, University of Michigan Abstract:For as long as people have studied geometry, they have counted In this talk, I will show how to solve several classical counting 
Thu Dec 06 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Dec 06 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Dec 06 
Student Number Theory Seminar12:20pm  Vincent Hall 313A Tour of the Modularity Theorem Katy Weber, University of Minnesota Abstract:The Modularity Theorem (also known as the TaniyamaShimuraWeil Conjecture) states, essentially, that every elliptic curve arises from a modular form. It is a special case of the Langlands correspondence and was a major part of Andrew Wiles' proof of Fermat's Last Theorem. In this talk, I will sketchily discuss the theorem in its various forms, leading up to the statement that the Lfunction of an elliptic curve agrees with the Lfunction of a modular form. Along the way, we will encounter some algebraic geometry words, e.g. "moduli space," "universal curve," and "sheaf." 
Thu Dec 06 
Climate Seminar11:15am  Vincent Hall 570Stability of traveling pulses in the FitzHughNagumo equations Paul Carter, University of Arizona Abstract:Traveling waves arise in partial differential equations in a broad range of applications, for instance chemical reactions, propagation of electrical signals, or the dynamics of traffic jams. The notion of stability of a traveling wave solution concerns its resilience to small perturbations and can usually be inferred from an eigenvalue problem obtained by linearizing the PDE about the solution. In this talk, I will discuss these ideas in the context of the FitzHughNagumo system, a simplified model of nerve impulse propagation. I will present existence and stability results for (multi)pulse solutions, and I will describe a phenomenon whereby unstable eigenvalues accumulate as a single pulse is continuously deformed into a double pulse 
Thu Dec 06 
Special Events and Seminars11:00am  Tate Hall B20padic local systems in padic geometry Koji Shimizu, University of California, Berkeley Abstract:An etale padic local system on a rigid analytic variety can be regarded as a family of padic Galois representations parametrized by the variety, and padic Hodge theory has brought many results and applications on such objects, including a padic RiemannHilbert correspondence by Diao, Lan, Liu and Zhu. I will discuss constancy of a key invariant (generalized HodgeTate weights) of general padic local systems 
Wed Dec 05 
PDE Seminar3:35pm  Vincent Hall 570Barotropic instability of shear flows Zhiwu Lin, Georgia Institute of Technology Abstract:We consider barotropic instability of shear flows for incompressible fluids with Coriolis effects. For a class of shear flows, we develop an approach by using the Hamiltonian structures of the linearized equation and an instability index formula to find the sharp stability conditions. We studied the flow with Sinus profile in details and found the sharp stability boundary in the whole parameter space, which corrected previous results in the fluid literature. The addition of the Coriolis force brings some fundamental changes to the stability of shear flows. Moreover, we also study the bifurcation of nontrivial traveling wave solutions and the linear inviscid damping near the shear flows. This is joint work with Hao Zhu and Jincheng Yang. 
Tue Dec 04 
Dynamical Systems2:30pm  Ford Hall 130Dynamical Systems Seminar 
Tue Dec 04 
Math Physics Seminar12:20pm  Vincent Hall 313Revivals and Fractalization in the Linear Free Space Schrödinger Equation with Pseudoperiodic Boundary Conditions Natalie Sheils Abstract:We consider the onedimensional linear free space Schrödinger equation on a bounded interval subject to homogeneous linear boundary conditions. We prove that, in the case of pseudoperiodic boundary conditions, the solution of the initialboundary value problem exhibits the phenomenon of revival at specific ("rational'') times, meaning that it is a linear combination of a certain number of copies of the initial datum. Equivalently, the fundamental solution at these times is a finite linear combination of delta functions. At other ("irrational'') times, for suitably rough initial data, e.g., a step or more general piecewise constant function, the solution exhibits a continuous but fractallike profile. Further, we express the solution for general homogeneous linear boundary conditions in terms of numerically computable eigenfunctions. (Joint work with Peter Olver and David Smith) 
Tue Dec 04 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Dec 04 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Dec 03 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1A Chebotarev density theorem for families of fields with an application to bounding ltorsion in class groups Caroline TurnageButterbaugh 
Mon Dec 03 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Interfaces with singularities: understanding phase transitions in nematic liquid crystals Dmitry Golovaty, Department of Mathematics, University of Akron Abstract:A nematic liquid crystal is essentially a liquid that exhibits some orientational order. The liquid crystalline state is typically observed in materials composed of highly asymmetric molecules for temperatures in the intermediate range when the material is neither a classical liquid nor a solid. In this talk we will be interested in describing a phase transition between the nematic and the isotopic state when the nematic order melts and the liquid crystal turns into a regular isotopic fluid. The experimental observations of this process indicate that the transition proceeds via evolution of interfaces separating different phases where the interfaces are generally not smooth. Our goal in this talk is to explain presence of these phase boundary singularities from a mathematical point of view . The nematictoisotopic phase transition can be described within the so called Landaude Genes variational theory for a tensorvalued order parameter. Because this theory is rather complex, in order to develop an initial understanding of transitions between the ordered and disordered states, we propose a simpler toy model based on the modified GinzburgLandautype energy defined over vector fields on the plane. The corresponding variational model consists of anisotropic gradient terms and a potential that vanishes on two disconnected sets. While this model may not quantitatively describe the nematic state, the topology of the simplified target set retains the crucial features of the full problem. The principal observation from the study of the simplified model is that the phase boundary singularities can be explained by large disparity between the elastic constants that specify the gradient contribution to the energy. In the talk we will present a combination of rigorous analysis and numerics that leads to this conclusion. 
Mon Dec 03 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Dec 03 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Nov 30 
MCFAM Seminar5:30pm  Vincent Hall 16The Effect of the Risk Corridors Program on Marketplace Premiums and Participation Pinar Karaca Mandic, MILI Director/Carlson Finance Professor Abstract:We investigate the effect of the Risk Corridors (RC) program 
Fri Nov 30 
Combinatorics Seminar3:35pm  Vincent Hall 570Grassmann Pentagram Maps and Noncommutative Integrable Systems Nicholas Ovenhouse, Michigan State University Abstract:The pentagram map is a discrete dynamical system on the space of plane polygons. Gekhtman, Shapiro, Tabachnikov, and Vainshtein used the combinatorics and Poisson geometry associated to certain networks/quivers on surfaces to prove that this map is integrable. Recently, MariBeffa and Felipe introduced a version of the pentagram map on Grassmannians, and found a Lax representation. I will generalize the techniques of Gekhtman et. al. to the Grassmann case, and show this gives a "formal" integrable system in a noncommutative algebra. 
Fri Nov 30 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Nov 30 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Nov 30 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Nov 30 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206The definition of Deligne's category Rep(S_t) Cecily Santiago, University of Minnesota Abstract:Following section 2.2 of the paper, On blocks of Deligne's category Rep(S_t), by Comes and Ostrik, we give the definition of this category and explore some of its first properties. 
Fri Nov 30 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Recap of MinneMUDAC: Challenges and Improvements ,  Abstract:Graduatelevel participants of 2018 MinneMUDAC data challenge will give an updated version of their original presentation, supplemented with suggestions for potential improvements to answering the challenge question, which was predicting the voter turnout for the 2018 midterm elections in Minnesota. After the talks, all participants will break into discussions regarding the presentations and the questions that arise from them. Speakers: Several teams that competed in MinneMUDAC 
Fri Nov 30 
MathCEP Seminar10:10am  Vincent Hall 364MathCEP Seminar 
Fri Nov 30 
Probability Seminar8:30am CANCELLED 
Thu Nov 29 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Nov 29 
Colloquium3:35pm  Vincent Hall 16Interpolative decomposition and its applications Lexing Ying, Stanford, Ordway Visitor Abstract:Interpolative decomposition is a simple and yet powerful tool for approximating lowrank matrices. After discussing the theory and algorithm, I will present a few new applications of interpolative decomposition in numerical partial differential equations, quantum chemistry, and machine learning. 
Thu Nov 29 
IMA Data Science Lab Seminar3:35pm  Vincent 16Interpolative Decomposition and its Applications (Math Dept Colloquium Lecture) Lexing Ying, Stanford University Abstract:Interpolative decomposition is a simple and yet powerful tool for approximating lowrank matrices. After discussing the theory and algorithm, I will present a few new applications of interpolative decomposition in numerical partial differential equations, quantum chemistry, and machine learning. 
Thu Nov 29 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Nov 29 
Commutative Algebra Seminar1:25pm  Ford Hall 170On invariant theory for "coincidental" reflection groups Victor Reiner, University of Minnesota Abstract:(joint work with A. Shepler and E. Sommers) 
Thu Nov 29 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Nov 29 
Student Number Theory Seminar12:20pm  Vincent Hall 313The Weil Conjectures: 0 to 100 Liam Keenan, University of Minnesota Abstract:The Weil conjectures are perhaps one of the most stunning achievements in arithmetic geometry in the 20th century. In this talk, I plan to introduce the necessary algebrogeometric language, state the conjectures, discuss the some of the tools used to prove them, and draw connections to analytic number theory. 
Thu Nov 29 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Thu Nov 29 
Colloquium10:00am  Vincent Hall 570The role of Energy in Regularity Max Engelstein, MIT Abstract:The calculus of variations asks us to minimize some energy and then describe the shape/properties of the minimizers. It is perhaps a surprising fact that minimizers to ``nice" energies are more regular than one, a priori, assumes. A useful tool for understanding this phenomenon is the EulerLagrange equation, which is a partial differential equation satisfied by the critical points of the energy. However, as we teach our calculus students, not every critical point is a minimizer. In this talk we will discuss some techniques to distinguish the behavior of general critical points from that of minimizers. We will then outline how these techniques may be used to solve some central open problems in the field. We will then turn the tables, and examine PDEs which look like they should be an EulerLagrange equation but for which there is no underlying energy. For some of these PDEs the solutions will regularize (as if there were an underlying energy) for others, pathological behavior can occur 
Wed Nov 28 
PDE Seminar3:30pm  Vincent Hall 570An Epiperimetric Approach to Isolated Singularities Max Engelstein, MIT Abstract:The presence of singular points (i.e. points around which the object in question does not look flat at any scale) is inevitable in most minimization problems. One fundamental question is whether minimizers have a unique tangent object at singular points i.e., is the minimizer increasingly well approximated by some other minimizing object as we zoom in at a singular point. This question has been investigated with varying degrees of success in the settings of minimal surfaces, harmonic maps and obstacle problems amongst others. In this talk, we will give the first uniqueness of blowups result for minimizers of the AltCaffarelli functional. In particular, we prove that the tangent object is unique at isolated singular points in the free boundary. Our main tool is a new approach to proving (log)epiperimetric inequalities at isolated singularities. This epiperimetric inequality differs from previous ones in that it holds without any additional assumptions on the symmetries of the tangent object. If we have time, we will also discuss how this method allows us to recover some uniqueness of blowups results in the minimal surfaces setting, particularly those of AllardAlmgren (81) and Leon Simon (83). This is joint work with Luca Spolaor (MIT) and Bozhidar Velichkov (U. Grenoble Alpes). 
Wed Nov 28 
IMA Data Science Lab Seminar1:25pm  Lind 305Convex Relaxation Approaches for Strictly Correlated Density Functional Theory Lexing Ying, Stanford University Abstract:In this talk, we introduce methods from convex optimization to solve the multimarginal transport type problems arise in the context of density functional theory. Convex relaxations are used to provide outer approximation to the set of Nrepresentable 2marginals and 3marginals, which in turn provide lower bounds to the energy. We further propose rounding schemes to obtain upper bound to the energy. 
Tue Nov 27 
Colloquium3:35pm  Vincent Hall 16Surface bundles, monodromy, and arithmetic groups Bena Tshishiku, Harvard University Abstract:Fiber bundles with fiber a surface arise in many areas including hyperbolic geometry, symplectic geometry, and algebraic geometry. Up to isomorphism, a surface bundle is completely determined by its monodromy representation, which is a homomorphism to a mapping class group. This allows one to use algebra to study the topology of surface bundles. Unfortunately, the monodromy representation is typically difficult to "compute" (e.g. determine its image). In this talk, I will discuss some recent work toward computing monodromy groups for holomorphic surface bundles, including certain examples of Atiyah and Kodaira. This can be applied to the problem of counting the number of ways that certain 4manifolds fiber over a surface. This is joint work with Nick Salter. 
Tue Nov 27 
Dynamical Systems2:30pm  Ford Hall 130Dynamical Systems Seminar  Eddie Nijholt  Cancelled Eddie Nijholt, UIUC Abstract:Network dynamical systems play an important role in many fields of science; whenever there are agents whose time evolution is linked through some interaction structure, we may view the system as a network and model it accordingly. However, despite their prevalence, network dynamical systems are in general not well understood. One can identify two reasons for this. First of all, many coordinate changes and other transformations from wellknown dynamical systems techniques do not respect the underlying network structure. Second of all, despite this somewhat `ethereal' character, systems with a network structure often display behavior that is highly anomalous for general dynamical systems. Examples of this include very unusual bifurcation scenarios and high spectral degeneracies. As a possible explanation of this, it can be shown that a large class of network ODEs admit hidden symmetry, which may be discovered through the socalled fundamental network construction. In most cases, this underlying symmetry does not come from a group though, but rather from a more general algebraic structure such as a monoid or category. I will show how the fundamental network allows one to adapt techniques from dynamical systems theory to a network setting, and how some of the more unusual properties of networks may be explained. In doing so, I will mostly focus on spectral properties of linear network maps. 
Tue Nov 27 
Math Physics Seminar12:20pm  Vincent Hall 313Math Physics Seminar 
Tue Nov 27 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Nov 27 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Nov 26 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Cuspforms with Compact Support [sic] Paul Garrett, University of Minnesota 
Mon Nov 26 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Nov 26 
Special Events and Seminars3:35pm  Vincent Hall 207Inverse transport theory and related applications RuYu Lai, University of Minnesota Abstract:The inverse transport problem consists of reconstructing the optical properties of a medium from boundary measurements. It finds applications in a variety of fields. In particular, radiative transfer equation (a linear transport equation) models the photon propagation in a medium in optical tomography. In this talk I will address results on the determination of these optical parameters. Moreover, the connection between the inverse transport problem and the Calderon problem will also be presented. 
Mon Nov 26 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: Cohomology of arithmetic groups and characteristic classes of manifold bundles Bena Tshishiku, Harvard University Abstract:A basic problem in the study of fiber bundles is to compute the ring H*(BDiff(M)) of characteristic classes of bundles with fiber a smooth manifold M. When M is a surface, this problem has ties to algebraic topology, geometric group theory, and algebraic geometry. We have a good understanding of the cohomology in the "stable range", but this accounts for a small percentage of the total cohomology, and little is known beyond that. In this talk I describe some new characteristic classes (in the case dim M >>0) that come from the unstable cohomology of arithmetic groups. 
Mon Nov 26 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Nov 26 
IMA Data Science Lab Seminar1:25pm  Lind 305Solving PDEs with Deep Learning Lexing Ying, Stanford University Abstract:In this talk, I will discuss some recent work on using deep neutral networks in solving high dimensional PDE problems. Examples include molecular dynamics, density functional theory, and inverse scattering problems. In each case, we propose novel neural network architectures based on the physical properties and sparse structures of the problem under investigation. 
Mon Nov 26 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Nov 23 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Nov 23 
Combinatorics Seminar3:35pm  Vincent Hall 570Combinatorics Seminar 
Fri Nov 23 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Nov 23 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Nov 23 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Nov 23 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Algebraic Representation Theory 
Fri Nov 23 
MathCEP Seminar10:10am  Vincent Hall 364MathCEP Seminar 
Fri Nov 23 
Probability Seminar8:30am CANCELLED 
Thu Nov 22 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Nov 22 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Nov 22 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Nov 22 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Nov 22 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Nov 22 
Student Number Theory Seminar12:20pm  Vincent Hall 313Student Number Theory TBA 
Thu Nov 22 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Nov 21 
PDE Seminar3:30pm  Vincent Hall 570PDE Seminar 
Tue Nov 20 
Dynamical Systems2:30pm  Ford Hall 130Dynamical Systems Seminar 
Tue Nov 20 
Math Physics Seminar12:20pm  Vincent Hall 313Application of Invariant Signatures: Solving Jigsaw Puzzles Rob Thompson Abstract:TBA 
Tue Nov 20 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Nov 20 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Nov 19 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Semigroups and automorphic forms Amy DeCelles, University of St. Thomas 
Mon Nov 19 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Divide and conquer algorithms and software for large Hermitian eigenvalue problems Yousef Saad, Department of Computer Science and Engineering, University of Minnesota Abstract:The solution of large symmetric real (or Hermitian complex) eigenvalue 
Mon Nov 19 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: The spectrum of units of a height 2 theory Jeremy Hahn, Harvard University Abstract:The space BSU admits two infinite loop space structures, one arising from addition of vector bundles and the other from tensor product. A surprising fact, due to Adams and Priddy, is that these two infinite loop spaces become equivalent after pcompletion. I will explain how the AdamsPriddy theorem allows for an identification of sl_1(ku_p), the spectrum of units of pcomplete complex Ktheory. I will then describe work, joint with Andrew Senger, that attempts to similarly understand the spectrum of units of the 2completion of tmf_1(3). 
Mon Nov 19 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Nov 19 
IMA Data Science Lab Seminar1:25pm  Lind 305Lipschitz Regularized Deep Neural Networks Converge and are Robust to Adversarial Perturbations Adam Oberman, McGill University Abstract:Deep Neural Networks perform well in practice, but unlike traditional Machine Learning methods, they lack performance guarantees. This limits the use of the technology in real world and real time applications. The first step towards these guarantees is a proof of generalization. We will prove that Lipschitz regularized DNNs converge, and provide a rate of convergence, a stronger result which implies generalization. The regularization is related to the classical Lipschitz extension problem, and to inverse problems in Image Processing. It can be implemented in practice, and leads to robust networks which are more resistant to adversarial examples. Joint work with Jeff Calder, available at https://arxiv.org/abs/1808.09540 Adam Oberman in a professor at McGill University. He studied at University of Toronto (Bachelors) and University of Chicago (PhD) before a postdoc at University of Texas, Austin, and a faculty position at Simon Fraser University. His research is on numerical methods for Partial Differential Equations, and more recently on optimization and Machine Learning. 
Mon Nov 19 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Nov 16 
MCFAM Seminar5:30pm  Vincent Hall 16No MCFAM Seminar 
Fri Nov 16 
Combinatorics Seminar3:35pm  Vincent Hall 570Cyclic Sieving, Necklaces, and Bracelets Eric Stucky, University of Minnesota Abstract:One of the many interpretations of Catalan numbers is that Cn counts necklaces with n white beads and n+1 black beads. Motivated by this, we generalize the Catalan numbers and their qanalogues to many other necklaces. In this talk, we will discuss two surprising properties of these generalizations. First, they exhibit a q=1 phenomenon with respect to necklace reflection, which can be extended to a cyclic sieving phenomenon for more exotic symmetries. Second, they conjecturally satisfy a "parityunimodality" property, which in classical cases is a combinatorial shadow of a certain sl2 representation. 
Fri Nov 16 
Probability Seminar2:30pm  Vincent Hall 209Macroscopic fluctuations through Schur generating functions Vadim Gorin, MIT Abstract:I will talk about a special class of largedimensional stochastic systems with strong correlations. The main examples will be random tilings, noncolliding random walks, eigenvalues of random matrices, and measures governing decompositions of group representations into irreducible components. 
Fri Nov 16 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Nov 16 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Nov 16 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Advanced Dynamics Systems Analysis and Synthesis for Future Storage Challenges Raye Sosseh, Seagate Technology Abstract:Seagate is the global leader in data storage solutions, developing amazing products that enable people and businesses around the world to create, share and preserve their most critical memories and business data. Over the years the amount of information stored has grown from megabytes all the way to geopbytes, confirming the need to successfully store and access huge amounts of data. As demand for storage technology grows the need for greater efficiency and more advanced capabilities continues to evolve. Today data storage is more than just archiving; its about providing ways to analyze information, understand patterns and behavior, to relive experiences and memories. Its about harnessing stored information for growth and innovation. Seagate is building on its heritage of storage leadership to solve the challenge of getting more out of the living information thats produced everyday. What began with one storage innovation has morphed into many systems and solutions becoming faster, more reliable and expansive. These considerations will be explored in this lecture on the application of Advanced Dynamics System Analysis & Synthesis to provide Solutions for future Storage Challenges. Bio 
Fri Nov 16 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Partition algebras and their action on tensor space  continuation Weiyan Chen, University of Minnesota Abstract:We continue with section 2.1 of the paper, On blocks of Delignes category Rep(S_t), by Comes and Ostrik. The longer term goal is to describe Deligne's category. In section 2.1 the partition algebras are introduced. They arose in work of Martin in a context of statistical mechanics, and were later shown by Jones to be in SchurWeyl duality with the group algebras of symmetric groups. The exposition is introductory. 
Fri Nov 16 
MathCEP Seminar10:10am  Vincent Hall 364MathCEP Seminar 
Fri Nov 16 
Probability Seminar8:30am CANCELLED 
Thu Nov 15 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Nov 15 
Colloquium3:35pm  Vincent Hall 16(Log)Epiperimetric Inequality and the Regularity of Variational Problems Luca Spolaor, MIT Abstract:In this talk I will present a new method for studying the regularity of minimizers to variational problems. I will start by introducing the notion of blowup, using as a model case the socalled Obstacle problem. Then I will state the (Log)epiperimetric inequality and explain how it is used to prove uniqueness of the blowup and regularity results for the solution near its singular set. I will then show the flexibility of this method by describing how it can be applied to other freeboundary problems and to (almost)area minimizing currents. Finally I will describe some future applications of this method both in regularity theory and in other settings. 
Thu Nov 15 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Nov 15 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Nov 15 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Nov 15 
Student Number Theory Seminar12:20pm  Vincent Hall 313Physics of the Riemannzeta function II Adrienne Sands, University of Minnesota Abstract:We continue to discuss how the Riemannzeta function plays a role in different areas of physics, from condensed matter theory to quantum mechanics 
Thu Nov 15 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Nov 14 
PDE Seminar3:30pm  Vincent Hall 570PDE Seminar 
Tue Nov 13 
Dynamical Systems2:30pm  Ford Hall 130Zigzagging of stripe patterns in growing domains Montie Avery, University of Minnesota Abstract:The SwiftHohenberg equation is a PDE which models formation of stripe and spot patterns in many physical settings. I will study a modification in which pattern formation is triggered by a propagating interface, and discuss the bifurcation structure based on the interface speed. I will focus on analytical results in reduced equations, in particular a singular perturbation problem for a system of ODEs arising from a traveling wave ansatz. I will also present numerical results in the SwiftHohenberg and reduced equations which organize the bifurcation structure into a twodimensional surface we call the moduli space. This is joint work with Ryah Goh, Oscar Goodloe, Alex Milewski, and Arnd Scheel. 
Tue Nov 13 
Math Physics Seminar12:20pm  Vincent Hall 313Math Physics Seminar 
Tue Nov 13 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Nov 13 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Nov 12 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Semigroups and uniqueness of solutions of differential equations in automorphic forms Amy DeCelles, University of St. Thomas 
Mon Nov 12 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Nov 12 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: Localizing the E_2 page of the Adams spectral sequence Eva Belmont, Northwestern Abstract:The Adams spectral sequence is one of the central tools for calculating the stable homotopy groups of spheres, one of the motivating problems in stable homotopy theory. In this talk, I will discuss an approach for computing the Adams E_2 page for the sphere at p = 3 in an infinite region, by computing its localization by the nonnilpotent element b_{10}. This approach relies on computing an analogue of the Adams spectral sequence in Palmieri's stable category of comodules, which can be regarded as an algebraic analogue of stable homotopy theory. This computation fits in the framework of chromatic homotopy theory in the stable category of comodules. 
Mon Nov 12 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Nov 12 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Rebecca Willett, University of Chicago 
Mon Nov 12 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Nov 09 
MCFAM Seminar5:30pm  Vincent Hall 16Macroecomic Analysis and Insight  Steepness of the Yield Curve As of September 2018 Ujae Kang, UnitedHealth Group Abstract:Ujae Kang will present on the Federal Reserve over the years and its influence on the yield curve. Then, he will cover what to expect from the Federal Reserve in the coming years. Bio: Ujae Kang is Director of Enterprise Risk Management at UnitedHealth Group. He is an Associate of the Society of Actuaries and has an Master of Financial Mathematics from the University of Minnesota's School of Mathematics. He also provides economic research and insights to UnitedHealth Group's Asset Liability Management Committee as well as to other investors. For more information on Ujae go to linkedin.com/in/ujaeaugustinekang 
Fri Nov 09 
Lie Theory Seminar3:35pm  Vincent Hall 313Motivic cohomology of Shimura varieties and level raising Rong Zhou, Institute for Advanced Study Abstract:For a finite type scheme over a field, its motivic cohomology groups were defined by Voevodsky and are an important algebraic invariant. However, the properties of these groups are not well understood, and it is a difficult problem to exhibit explicit classes in motivic cohomology. We will construct such classes in the special fiber of Hilbert modular varieties by using the geometry of the supersingular locus. The construction is related to a geometric realization of the JacquetLanglands correspondence, as well as to level raising for Hilbert modular forms. A key ingredient is a form of Ihara's Lemma for compact quaternionic Shimura surfaces. 
Fri Nov 09 
Combinatorics Seminar3:35pm  Vincent Hall 570Combinatorics Seminar 
Fri Nov 09 
Probability Seminar2:30pm  Vincent Hall 209Lowtemperature localization of directed polymers Erik Bates, Stanford University Abstract:On the ddimensional integer lattice, directed polymers are paths of a random walk that have been reweighted according to a random environment that refreshes at each time step. The qualitative behavior of the system is governed by a temperature parameter; if this parameter is small, the environment has little effect, meaning all possible paths are close to equally likely. If the parameter is made large, however, the system undergoes a phase transition at which the paths endpoint starts to localize. To understand the extent of this localization, we exploit the underlying Markov structure of the quenched endpoint distribution. The key difficulty is that the space of measures is too large for one to expect convergence results. By adapting methods appearing in the work of Mukherjee and Varadhan, we develop a compactification theory to resolve the issue. In this talk, we will discuss this intriguing abstraction, as well as new concrete theorems it allows us to prove for directed polymers constructed from SRW or any other walk. (joint work with Sourav Chatterjee) 
Fri Nov 09 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Nov 09 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Partition algebras and their action on tensor space Weiyan Chen, University of Minnesota Abstract:We follow section 2.1 of the paper, On blocks of Delignes category Rep(S_t), by Comes and Ostrik. The longer term goal is to describe Deligne's category. In section 2.1 the partition algebras are introduced. They arose in work of Martin in a context of statistical mechanics, and were later shown by Jones to be in SchurWeyl duality with the group algebras of symmetric groups. We introduce this theory. 
Fri Nov 09 
MathCEP Seminar10:10am  Vincent Hall 364The Distributed Open Education Network (Doenet) and your dream educational technology Duane Nykamp, University of Minnesota Abstract:A group of us are developing educational technology as part of the 
Fri Nov 09 
Probability Seminar8:30am CANCELLED 
Thu Nov 08 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Nov 08 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Nov 08 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Nov 08 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Nov 08 
Special Events and Seminars1:25pm  Vincent Hall 313Irreducible components of affine DeligneLusztig varieties and orbital integrals Rong Zhou, Institute for Advanced Study Abstract:Affine DeligneLusztig varieties (ADLV) naturally arise in the study of Shimura varieties and RapoportZink spaces. Their irreducible components provide an interesting class of cycles on the special fiber of Shimura varieties. We prove a conjecture of Miaofen Chen and Xinwen Zhu, which relates the number of irreducible components of ADLV's to a certain weight multiplicity for a representation of the Langlands dual group. Our approach is to count the number of F_q points as q goes to infinity; this boils down to computing a certain twisted orbital integral. After applying techniques from local harmonic analysis, we reduce to computing a particular coefficient of the matrix for the inverse Satake transform. Using an interpretation of this coefficient in terms of a qanalogue of Kostant's partition function, we are able to reduce the problem to the previously known special cases of the conjecture proved by HamacherViehmann and Nie. This is joint work with Yihang Zhu. 
Thu Nov 08 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Nov 08 
Student Number Theory Seminar12:20pm  Vincent Hall 313Physics of the Riemannzeta function Adrienne Sands, University of Minnesota Abstract:I will give an overview of how the Riemannzeta function plays a role in different areas of physics, from condensed matter theory to quantum mechanics. 
Thu Nov 08 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Nov 07 
PDE Seminar3:30pm  Vincent Hall 570PDE Seminar 
Tue Nov 06 
Dynamical Systems2:30pm  Ford Hall 130Dynamical Systems Seminar 
Tue Nov 06 
Math Physics Seminar12:20pm  Vincent Hall 313Contact Point Forces Acting on a Ball, Rolling on a Horizontal Plane and Actuated by Internal Point Masses Stuart Rogers Abstract:This talk derives the contact point forces, namely the normal force and static friction, that act on a ball rolling without slipping on a horizontal plane. It is assumed that the ball is actuated by n point masses, which are free to move inside the ball. The dynamics of a disk and ball actuated by internal point masses are simulated numerically and the minimum coefficients of static friction required to prevent slippage are computed 
Tue Nov 06 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Nov 06 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Nov 05 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Semigroups and uniqueness argument for solutions of differential equations in automorphic forms Amy DeCelles, St. Thomas University 
Mon Nov 05 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Nov 05 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: An isovariant Elmendorf's theorem Sarah Yeakel, University of Maryland Abstract:An isovariant map is an equivariant map which preserves isotropy groups. Isovariant maps show up in equivariant surgery theory and in other settings when homotopy theory is applied to geometry. For a finite group G, we consider the category of Gspaces with morphisms given by isovariant maps. We will discuss a cofibrantly generated model structure on this category, along with isovariant versions of Elmendorf's theorem and a theorem of Klein and Williams about homotoping a map off a submanifold. 
Mon Nov 05 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Nov 05 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Matthew Jacobs, University of California, Los Angeles 
Mon Nov 05 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Nov 02 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Nov 02 
Combinatorics Seminar3:35pm  Vincent Hall 570Enumerating factorizations in GL_n(F_q) Graham Gordon, University of Washington Abstract:Recently, many people, including Huang, Lewis, Morales, Reiner, and Stanton, have enumerated certain factorizations in GLnFq. Much of their results are essentially qanalogues of factorization enumerations coming from Sn in the q>1 sense. I think this work constitutes a few significant puzzle pieces in an enormous, really difficult puzzle. I will talk about another piece (or fraction of a piece) of this puzzle that I can contribute, which is an enumeration of factorizations of the identity into a product of regularelliptic elements. Ideally, this is qanalogous to a result of Stanley from the 1981, which enumerates factorizations of the identity into a product of ncycles. Time permitting, I will talk about my approach and/or the geometry that corresponds to this work. 
Fri Nov 02 
Probability Seminar2:30pm  Vincent Hall 209Dynamical freezing in a spin glass system with logarithmic correlations Julian Gold, Northwestern University Abstract:We consider a continuous time random walk on the twodimensional discrete torus, whose motion is governed by the discrete Gaussian free field on the corresponding box acting as a potential. More precisely, at any vertex the walk waits an exponentially distributed time with mean given by the exponential of the field and then jumps to one of its neighbors, chosen uniformly at random. We prove that throughout the lowtemperature regime and at inequilibrium timescales, the process admits a scaling limit as a spatial Kprocess driven by a random trapping landscape, which is explicitly related to the limiting extremal process of the field. Alternatively, the limiting process is a supercritical Liouville Brownian motion with respect to the continuum Gaussian free field on the box. Joint work with Aser Cortines (University of Zurich) and Oren Louidor (Technion). 
Fri Nov 02 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Nov 02 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Nov 02 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 409Lecture Joao Montero, Medtronic 
Fri Nov 02 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Topology and combinatorics of the complex of injective words  continuation Victor Reiner, University of Minnesota Abstract:I will continue the elementary treatment of properties of this complex, indicating situations where it arises, including a context considered by myself and Peter Webb. 
Fri Nov 02 
MathCEP Seminar10:10am  Vincent Hall 364MathCEP Seminar 
Fri Nov 02 
Probability Seminar9:30am CANCELLED 
Thu Nov 01 
Student Combinatorics Seminar4:40pm  Vincent Hall 570My favorite facts about $\mathrm{GL}_n \mathbb{F}_q$ Graham Gordon, University of Washington Abstract:Have you ever heard that the symmetric group $\mathfrak{S}_n$ is equal to the finite general linear group $\mathrm{GL}_n \mathbb{F}_q$ in the limit $q \to 1$? This equality casts many mathematical shadows. I will discuss some of my favorites, which involve the (complex) characters of the two groups. I will include a primer on $\mathrm{GL}_n \mathbb{F}_q$ characters, and I will assume some foundational representation theory facts. Next, I will turn the tides and consider the limit $q \to \infty$. Mysteriously, some relationship between $\mathrm{GL}_n \mathbb{F}_q$ and $\mathfrak{S}_n$ as $q \to \infty$ is also casting shadows. Time permitting, I will discuss how character theory can be used to enumerate factorizations in order to segue into tomorrows seminar. 
Thu Nov 01 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Nov 01 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Nov 01 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Nov 01 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Nov 01 
Student Number Theory Seminar12:20pm  Vincent Hall 313The Stonevon Neumann Theorem Joe Dickinson, University of Minnesota Abstract:I plan to talk about some number theoretic implications of the Stonevon Neumann theorem. The Stonevon Neumann theorem is a uniqueness theorem about commutation relations between position and momentum operators. I will give a historical discussion about number theory results implied by Stonevon Neumann. 
Thu Nov 01 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Oct 31 
PDE Seminar3:30pm  Vincent Hall 570On the global regularity for EinsteinKleinGordon coupled system Alexandru Ionescu, Princeton University Abstract:I will discuss the EinsteinKleinGordon coupled system of General 
Tue Oct 30 
Dynamical Systems2:30pm  Ford Hall 130Dynamical Systems Seminar 
Tue Oct 30 
Math Physics Seminar12:20pm  Vincent Hall 313Math Physics Seminar 
Tue Oct 30 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Oct 30 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Oct 29 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Semigroups and uniqueness arguments for solutions of differential equations in automorphic forms Amy DeCelles, St. Thomas University 
Mon Oct 29 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Preconditioning systems of PDEs: from robust estimates to fast iterations, with applications to simulations of the brain Ragnar Winther, University of Oslo Abstract:We will present a set up for simulations of the socalled glymphatic system, which is believed to 
Mon Oct 29 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: Symmetric monoidal categories and \Gammacategories Amit Sharma, Kent State University Abstract:A \Gammacategory is a functor from the category of finite based sets and basepoint preserving functions \Gamma^op to Cat. We construct a model category structure on the category of \Gammacategories, which is symmetric monoidal closed to the Day convolution product. The fibrant objects in this model category structure are those References: 
Mon Oct 29 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Oct 29 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Pratik Chaudhari, University of California, Los Angeles 
Mon Oct 29 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Oct 26 
MCFAM Seminar5:30pm  Vincent Hall 16Dynamic Linear Models Katy Micek, 3M Finance Abstract:Dynamic linear models (DLMs), a subset of state space models, describe the output of a dynamic system as a function of a nonobservable state process affected by random errors. Because DLMs can be used either for traditional time series analysis tasks (making inferences on observed states or prediction future observations) or for feature generation in machine learning tasks, they are a very useful tool for any data scientist who works with time series data. As a data scientist on the Data Analytics team for 3M Finance, I work primarily with time series data from the general ledger. Our team both leads data science projects and assists in organizational development of internal capabilities around data science. 
Fri Oct 26 
Algebraic Geometry3:35pm  Vincent Hall 313On rigid varieties with projective reduction Shizhang Li, Columbia University Abstract:Bosch, Lütkebohmert and Raynaud laid down the foundation relating formal and rigid geometry. The type of questions they treat are mostly concerned with going from the rigid side to formal side. In the past, I considered the opposite type of question, namely to what extent properties on the formal side inform us about rigid geometry. More precisely, we will see what geometric consequences one can deduce under the assumption that the rigid space has a projective reduction. In this talk, I shall first say some background of rigid geometry and Raynaud's theory of formal models along with some examples. Then I will state the main theorem and a corollary. If time permitted, I will say something about the proof. 
Fri Oct 26 
Combinatorics Seminar3:35pm  Vincent Hall 570High acyclicity of psubgroup complexes for the symmetric groups Cihan Bahran, University of Minnesota Abstract:For any finite group G and a fixed prime p, the topology of the poset of nontrivial elementary abelian psubgroups contains significant information about the representations of G in characteristic p. For the symmetric group, this poset and its homology remain rather mysterious. A reasonable conjecture is that as we consider larger symmetric groups, the associated posets should get topologically more connected. I will rephrase this conjecture as a representation stability phenomenon ala ChurchEllenbergFarb, and provide evidence for it by exhibiting high acyclicity of certain subposets.t: 
Fri Oct 26 
Probability Seminar2:30pm  Vincent Hall 209Some Problems of Robust Highdimensional Statistics Gilad Lerman, University of Minnesota Abstract:The talk will first review the problem of robust subspace recovery, which seeks an underlying lowdimensional subspace in a data set that is possibly corrupted with outliers. The emphasis will be on surveying existing theoretical guarantees and tradeoffs. New results for adversarial outliers will also be mentioned. Following this, other related problems will be discussed, along with new results for one of these problems. 
Fri Oct 26 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Oct 26 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Oct 26 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206Topology and combinatorics of the complex of injective words Victor Reiner, University of Minnesota Abstract:According to a result of Farmer, the homology of this complex vanishes except in the bottom and top dimensions. This property is a consequence of shellability of the complex. We will discuss these matters, used in a proof of Nakaoka's theorem on stability of the corestriction map in the group homology of the symmetric groups. 
Fri Oct 26 
MathCEP Seminar10:10am  Vincent Hall 364The Chicago Guide to Writing about Numbers Book Discussion Journal Club Abstract:People who work well with numbers are often stymied by how to write about them. Those who don't often work with numbers have an even tougher time trying to put them into words. For instance, scientists and policy analysts learn to calculate and interpret numbers, but not how to explain them to a general audience. Students learn about gathering data and using statistical techniques, but not how to write about their results. And readers struggling to make sense of numerical information are often left confused by poor explanations. Jane Miller, an experienced research methods and statistics teacher, gives writers the assistance they need. The Chicago Guide to Writing about Numbers helps bridge the gap between good quantitative analysis and good expository writing. Fieldtested with students and professionals alike, this book shows writers how to think about numbers during the writing process. By providing basic guidelines for successfully using numbers in prose, The Chicago Guide to Writing about Numbers will help writers of all kinds clearly and effectively tell a story with numbers as evidence. 
Fri Oct 26 
Probability Seminar9:30am CANCELLED 
Thu Oct 25 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Oct 25 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Oct 25 
Algebraic Geometry1:25pm  Vincent Hall 313An example of liftings with different Hodge numbers Shizhang Li, Columbia University Abstract:Does a smooth proper variety in positive characteristic know the Hodge numbers of its liftings? The answer is "of course not". However, it's not that easy to come up with a counterexample. In this talk, I will first introduce the background of this problem. Then I shall discuss some obvious constraints of constructing a counterexample. Lastly I will present such a counterexample and state a few questions of similar flavor for which I do not know an answer. 
Thu Oct 25 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Oct 25 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Oct 25 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Oct 25 
Student Number Theory Seminar12:20pm  Vincent Hall 313Cryptographic Multilinear Maps from Elliptic Curves Mahrud Sayrafi, University of Minnesota Abstract:We will begin with defining cryptographic multilinear maps, briefly discussing some of their applications, and referencing one such map from BonehSilverberg '03. After that, we will extend a problem involving isogenies of elliptic curves into an open problem of finding cryptographic invariant maps from Boneh, et al. '18.stract: 
Thu Oct 25 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Oct 24 
PDE Seminar3:30pm  Vincent Hall 570PDE Seminar 
Tue Oct 23 
Dynamical Systems2:30pm  Ford Hall 130Snaking in the SwiftHohenberg Equation in Dimension 1+Epsilon Jason Bramburger, Brown University Abstract:The SwiftHohenberg equation is a widely studied partial differential equation which is known to support a variety of spatially localized structures. The onedimensional equation exhibits spatially localized steadystate solutions which give way to a bifurcation structure known as snaking. That is, these solutions bounce between two different values of the bifurcation parameter while ascending in norm. The mechanism that drives snaking in one spatial dimension is now wellunderstood, but recent numerical investigations indicate that upon moving to two spatial dimensions, the related radiallysymmetric spatiallylocalized solutions take on a significantly different snaking structure which consists of three major components. To understand this transition we apply a dimensional perturbation in an effort to use welldeveloped methods of perturbation theory and dynamical systems. In particular, we are able to identify key characteristics that lead to the segmentation of the snaking branch and therefore provide insight into how the bifurcation structure changes with the spatial dimension. 
Tue Oct 23 
Math Physics Seminar12:20pm  Vincent Hall 313Math Physics Seminar 
Tue Oct 23 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Oct 23 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Oct 22 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Automorphic Hamiltonians Adrienne Sands, University of Minnesota Abstract:We apply methods of quantum mechanics to construct selfadjoint, purely discrete pseudodifferential operators which characterize a nuclear Frechet Schwartz space of automorphic forms. 
Mon Oct 22 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Oct 22 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: Finitely generated sequences of linear subspace arrangements Nir Gadish, University of Chicago Abstract:Hyperplane arrangements are a classical meeting point of topology, combinatorics and representation theory. Generalizing to arrangements of linear subspaces of arbitrary codimension, the theory becomes much more complicated. However, a crucial observation is that many natural sequences of arrangements seem to be defined using a finite amount of data. In this talk I will describe a notion of 'finitely generation' for collections of arrangements, unifying the treatment of known examples. Such collections turn out to exhibit strong forms of stability, both in their combinatorics and in their cohomology representation. This structure makes the appearance of representation stability transparent and opens the door to generalizations. 
Mon Oct 22 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Oct 22 
IMA Data Science Lab Seminar1:25pm  Lind 409Large Sample Asymptotics of Graphbased Methods in Machine Learning: Mathematical Analysis and Implications Nicolas GarciaTrillos, University of Wisconsin, Madison Abstract:Many machine learning procedures aimed to extract information from data can be defined as precise mathematical objects that are constructed in terms of the data. It is often assumed that the data is big in complexity but also in quantity, and in this large amount of data setting, a basic mathematical concept that one can explore is that of closure of a given class of statistical procedures (i.e. what are the limiting procedures as the number of data points available goes to infinity.) In this talk, I will explore this notion in the context of graphbased methods. Examples of such methods include minimization of Cheeger cuts, spectral clustering, and graphbased bayesian semisupervised learning, among others. I will introduce some of the mathematical ideas needed for the analysis, as well as show some of the implications of it: our results show statistical consistency of the methods, provide with quantitative information in the form of scaling of parameters and rates of convergence, imply qualitative properties at the discrete level, and suggest the use of appropriate algorithms. 
Mon Oct 22 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Oct 19 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Oct 19 
Lie Theory Seminar4:30pm  Vincent Hall 313On Several Classical Number Theory Problems Tianxin Cai, Zhejiang University and University of Iowa 
Fri Oct 19 
Combinatorics Seminar3:35pm  Vincent Hall 570Optimal switching sequence for switched linear systems Qie He, UMN Abstract:We study the following optimization problem over a dynamical system that consists of several linear subsystems: Given a finite set of nbyn real matrices and an ndimensional real vector, find a sequence of K matrices, each chosen from the given set of matrices, to maximize a convex function over the product of the K matrices and the given vector. This simple problem has many applications in operations research and control, yet a moderatesized instance is challenging to solve to optimality for stateoftheart optimization software. We propose a simple exact algorithm for this problem. The efficiency of our algorithm depends heavily on whether the given set of matrices has the oligovertex property, a concept we introduce for a finite set of matrices. The oligovertex property captures how the numbers of extreme points for a sequence of K convex polytopes related to the given matrices grow with respect to K. We derive several sufficient conditions for a set of matrices to have this property, and pose several open questions related to this property. 
Fri Oct 19 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Oct 19 
Differential Geometry and Symplectic Topology Seminar2:30pm  Vincent Hall 6The Smooth 4dimensional Poincare Conjecture and Dehn surgery on links Alex Zupan, University of Nebraska Abstract:The smooth version of the 4dimensional Poincare Conjecture (S4PC) states that every homotopy 4sphere is diffeomorphic to the standard 4sphere. One way to attack the S4PC is to examine a restricted class of 4manifolds. For example, Gabai's proof of Property R implies that every homotopy 4sphere built with one 2handle and one 3handle is standard. In this talk, we consider homotopy 4spheres X built with two 2handles and two 3handles, which are uniquely determined by the attaching link L for the 2handles in the 3sphere. We prove that if one of the components of L is the connected sum of a torus knot T(p,2) and its mirror (a generalized square knot), then X is diffeomorphic to the standard 4sphere. This is joint work with Jeffrey Meier. 
Fri Oct 19 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Oct 19 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206A theorem of Nakaoka on the homology of symmetric groups  continuation Peter Webb, University of Minnesota Abstract:A theorem of Nakaoka states that the inclusion of symmetric groups induces an isomorphism of group homology provided that the degrees of the symmetric groups are large enough. This week I will continue with the proof of this, explaining the equivariant cohomology spectral sequence and the specific calculations that arise, trying to assume as little as I can. 
Fri Oct 19 
MathCEP Seminar10:10am  Vincent Hall 364MathCEP Seminar 
Fri Oct 19 
Probability Seminar9:30am CANCELLED 
Thu Oct 18 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Oct 18 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Oct 18 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Oct 18 
Commutative Algebra Seminar1:25pm  Ford Hall 170Computations in Local Rings using Macaulay2 Mahrud Sayrafi, University of Minnesota Abstract:Local rings are ubiquitous in commutative algebra and algebraic geometry. In this talk I will describe two avenues for computing in local rings with respect to prime ideals, first using the associated graded algebra and then using only Nakayama's lemma. Time permitting, I will demonstrate various examples and applications, such as computing the HilbertSamuel multiplicity, using Macaulay2. 
Thu Oct 18 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Oct 18 
Student Number Theory Seminar12:20pm  Vincent Hall 313Elliptic functions and elliptic curves in the 19th century Devadatta Hegde, University of Minnesota Abstract:We will give an account of the work on Weierstrass and Jacobi proving a result due to Abel on meromorphic functions on the torus. These are results about complex points of elliptic curves which suggest attributes for rational points. These examples were later greatly extended at the hands of several mathematicians and reached a highpoint with the GAGA principle by Serre. It's also the first example of a RiemannRoch type theorem which were greatly extended by Grothendieck, Atiyah and Singer. Only some familiarity with Cauchy's theorem in complex analysis is needed to understand the talk. 
Thu Oct 18 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Oct 17 
PDE Seminar3:30pm  Vincent Hall 570Continuum Limits of SemiSupervised Learning on Graphs Matthew Thorpe, University of Cambridge Abstract:Given a data set $\{x_i\}_{i=1}^n$ with labels $\{y_i\}_{i=1}^N$ on the first $N$ data points the goal of semisupervised is to infer labels on the remaining $\{x_i\}_{i=N+1}^n$ data points. In this talk we use a random geometric graph model with connection radius $r(n)$. The framework is to consider objective functions which reward the regularity of the estimator function and impose or reward the agreement with the training data, more specifically we will consider discrete pLaplacian and fractional Laplacian regularization. The talk concerns the asymptotic behaviour in the limit where the number of unlabelled points increases while the number of training points remains fixed. The results are to uncover a delicate interplay between the regularizing nature of the functionals considered and the nonlocality inherent to the graph constructions. I will give almost optimal ranges on the scaling of $r(n)$ for asymptotic consistency to hold. Furthermore, I will setup the Bayesian interpretation of this problem. This is joint work with Matt Dunlop (Caltech), Dejan Slepcev (CMU) and Mathew Thorpe is a Research Fellow at the Cantab Capital Institute for the Mathematics of Information, Department of Applied Mathematics and Theoretical Physics, University of Cambridge. . 
Tue Oct 16 
Dynamical Systems2:30pm  Ford Hall 130Runandtumble clusters: blowing up the blowup Arnd Scheel Abstract:Motivated by patterns in colonies of myxobacteria, I will show some results on clustering in runandtumble processes. We look at two populations of agents on the real line, propagating with speed 1 to the left or to the right, respectively. They tumble, that is, reverse direction, with a rate that depends on encounters with agents traveling in the opposite direction in a nonlinear fashion. I will show some phenomena and then explain how elementary dynamical systems methods can help understanding the formation of localized clusters in the population. The talk should be accessible to graduate students with basic knowledge in dynamical systems 
Tue Oct 16 
Math Physics Seminar12:20pm  Vincent Hall 313Math Physics Seminar 
Tue Oct 16 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Oct 16 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Oct 15 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Automorphic Hamiltonians Adrienne Sands, University of Minnesota Abstract:We apply methods in quantum mechanics to construct selfadjoint, purely discrete pseudodifferential operators which characterize a nuclear Fréchet Schwartz space of automorphic forms" 
Mon Oct 15 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Modeling gas, fluid, and particle transport in the lung airway system: the curse of scales Marcel Filoche, Ecole Polytechnique, Paris Abstract:The pulmonary airway system is a highly hierarchical treelike 3D network in charge of transferring oxygen from the upper airways down to the alveolar region where the gas exchange occurs between air and blood. It is also the place of numerous particle and fluid transport processes. Given the complexity of the anatomy and of the physics involved, numerical simulation is a remarkable tool for investigating the properties of this organ seen as a "transport system", understanding its behavior and possible failures, and predicting the outcome of therapies. However, the range of scales represents here a huge challenge: from the meter scale of the entire organ size down to the micron scale of the mucus layer, about 5 to 6 orders of magnitude of length scale are crossed. In this talk, we will present several examples of numerical models able to capture the various aspects of the lung airway system, from the simplest linear approach of gas transport to more advanced computational fluid dynamics simulation. We will show, in particular, how the range of scales involved and the difficulty to access the actual parameters in the patient imposes to use a hierarchy of models and a diversity of numerical techniques. We will explain how these models can be used either to reach a general understanding of the system or to design patient specific diagnosis and therapy. 
Mon Oct 15 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: Rigidity of warped cones and coarse geometry of expanders Wouter van Limbeek, UIC Abstract:Finitely generated subgroups of compact Lie groups give rise to expander graphs via a warped cone construction. We study the dependence of the coarse geometry of such expander graphs on the original subgroup and establish a dynamical analogue of quasiisometric rigidity theorems in geometric group theory: Namely, the coarse geometry of the warped cone determines the subgroup up to commensurability, unless the group has abelian factors. This is joint work with David Fisher and Thang Nguyen. 
Mon Oct 15 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Oct 15 
IMA Data Science Lab Seminar1:25pm  Keller 3180Lecture Raj Nadakuditi, University of Michigan 
Mon Oct 15 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Oct 12 
MCFAM Seminar5:30pm  Vincent Hall 16Interpreting Constraints in Mean Variance Optimization Chris Bemis, Head of Quantitative Analysis and Research, Whitebox Advisors, UMN Math Dpt. Affiliated Faculty Abstract:We study the effect linear constraints have on risk in the context of mean variance optimization (MVO). Jagannathan and Ma (2003) establish an equivalence between certain constrained and unconstrained MVO problems via a modification of the covariance matrix. We extend their results to arbitrary linear constraints and provide alternative interpretations for the effect of constraints on both the input parameters to the problems at hand and why expost performance is improved in the constrained setting. 
Fri Oct 12 
Combinatorics Seminar3:35pm  Vincent Hall 570Basis shape loci and the positive Grassmannian Cameron Marcott, University of Waterloo Abstract:We study the set of kdimensional planes in Rn admitting a basis of vectors with prescribed supports. We describe conditions on the prescribed support shape for when this set of planes has the expected dimension in the Grassmannian, and for when this set of planes intersects the positive Grassmannian in its full dimension. 
Fri Oct 12 
Probability Seminar2:30pm  Vincent Hall 209BrascampLieb inequalities for even functions Liran Rotem, UMN Abstract:It was observed by CorderoErausquin, Fradelizi and Maurey that the classical Gaussian Poincare Inequality can be improved by a factor of 2 if we restrict our attention to even functions. They used this improved inequality to answer a geometric question asked by Banaszczyk about convexity of the Gaussian measure. The Gaussian Poincare inequality is a special case of a more general variance inequality due to Brascamp and Lieb. In general, it is not clear how to improve this more general inequality in the even case. Again, this question turns out to be closely related to certain geometric problems. In this talk we will prove a sharp even BrascampLieb inequality for measures of the form exp(x^p). To do so we will also present a new weighted Poincare inequality which holds for ODD functions. Based on joint work with Dario CorderoErausquin. 
Fri Oct 12 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Oct 12 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Oct 12 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Lecture Jennifer Schumacher, 3M 
Fri Oct 12 
Algebraic Representation Theory Seminar1:25pm  Vincent Hall 206A theorem of Nakaoka on the homology of symmetric groups Peter Webb, University of Minnesota Abstract:A theorem of Nakaoka states that the inclusion of symmetric groups induces an inclusion of group homology provided that the degrees of the symmetric groups are large enough. A proof of this statement in homological stability can be given using the equivariant cohomology of the complex of injective words. I will start describing the machinery needed to give this proof, trying to assume as little as I can. 
Fri Oct 12 
MathCEP Seminar10:10am  Vincent Hall 364Adventures with experiential and active learning Rina Ashkenazi, University of Minnesota Abstract:I will share my attempts to include real world experiences and active learning in the actuarial mathematics curriculum. Those include a design of a project based course (MATH 4067W) that is instructed in collaboration with practicing actuaries, as well as the inclusion of small projects and inclass presentations in other, existing courses. 
Fri Oct 12 
Probability Seminar9:30am CANCELLED 
Thu Oct 11 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Oct 11 
Colloquium3:35pm  Vincent Hall 16Propagation of bistable fronts through a perforated wall Hiroshi Matano, Meiji University, Tokyo, Ordway Visitor Abstract:We consider a bistable reactiondiffusion equation on ${\bf R}^N$ in the presence of an obstacle $K$, which is a wall of infinite span with periodically arrayed holes. More precisely, $K$ is a closed subset of ${\bf R}^N$ with smooth boundary such that its projection onto the $x_1$axis is bounded, while it is periodic in the rest of variables $(x_2,\ldots, x_N)$. We assume that ${\bf R}^N \setminus K$ is connected. Our goal is to study what happens when a planar traveling front coming from $x_1 = +\infty$ meets the wall $K$. We first show that there is clear dichotomy between `propagation' and `blocking'. In other words, the traveling front either completely penetrates through the wall or is totally blocked, and that there is no intermediate behavior. This dichotomy result will be proved by what we call a De Giorgi type lemma for an elliptic equation on ${\bf R}^N$. Then we will discuss sufficient conditions for blocking, and those for propagation. This is joint work with Henri Berestycki and Francois Hamel. 
Thu Oct 11 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Oct 11 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Oct 11 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Oct 11 
Student Number Theory Seminar12:20pm  Vincent Hall 313Student Number Theory TBA 
Thu Oct 11 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Oct 10 
PDE Seminar3:35pm  Vincent Hall 570Soliton resolution for the critical nonlinear heat equation Hiroshi Matano, Meiji University Abstract:In this talk, I will discuss the asymptotic behavior of radially symmetric solutions of the nonlinear heat equation on ${\bf R}^N$ $(N > 2)$ with the Sobolev critical power nonlinearity. In the case of timeglobal solutions, we show that the solution is asymptotically decomposed into a finite sum of rescaled ground states that hardly interact with each other because the ratio of the rescaling parameters of different solitons tends to infinity. The total energy of the solution then converges to an integer multiple of the energy of the ground state. We call this behavior ``soliton resolution" of the solution. In the case where the solution blows up in finite time, and if the blowup is of type II in a certain sense, we show that a similar soliton resolution occurs near the blowup point. Finally we will show the existence of a multisoliton timeglobal solution for the case $N > 6$. This is joint work with Frank Merle. 
Tue Oct 09 
Dynamical Systems2:30pm  Ford Hall 130Dynamical Systems Seminar 
Tue Oct 09 
Math Physics Seminar12:20pm  Vincent Hall 313Signal Processing and Classification Jimmy Broomfield Abstract:This talk will center around signal classification and it will include a demonstration in python. We will focus on how exploring three major 
Tue Oct 09 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Oct 09 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Oct 08 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Two applications of differential equations to automorphic forms Kim KlingerLogan, University of Minnesota 
Mon Oct 08 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Oct 08 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: A chromatic approach to tmf cooperations Paul van Koughnett, Purdue Abstract:The topological modular forms spectrum, tmf, is a cohomology theory constructed from elliptic curves that captures information about stable homotopy at chromatic heights less than or equal to 2. We present a description of the height 1 part of the algebra of tmf cooperations, and interpret it in terms of modular forms. This is joint work with Dominic Culver. 
Mon Oct 08 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Oct 08 
IMA Data Science Lab Seminar1:25pm  Lind 305A PDE Approach to a Prediction Problem Involving Randomized Strategies Nadejda Drenska, University of Minnesota, Twin Cities Abstract:This work investigates a classical problem from online machine learning using methods from optimal control theory. The problem is a discrete time iterative process involving decision making at every step; the goal for mathematical analysis is to understand the optimal strategy and its consequences over a long period of time. The solution is analyzed through its continuous limitan appropriately defined value function, which solves a PDE in the viscosity sense. The PDE is then used to determine the optimal strategies. Bio 
Mon Oct 08 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Oct 05 
MCFAM Seminar5:30pm  Vincent Hall 16CCAR (Comprehensive Capital Analysis and Review) and Basel Framework  Risk Management Modeling Dr. Xu Li Abstract:Dr.Xu Li will give an overview of what he is does in Market Risk Analytics as a SVP of Risk Analytics at Citi. He will then focus on a default model that is useful for both CCAR, the stress testing framework set out by the Federal Reserve (IDR) and Basel framework which is the international regulatory framework for banks (IRC, DRC). He will show the general ideas on modeling the default risks and discuss some options on the modeling choices. 
Fri Oct 05 
Combinatorics Seminar3:35pm  Vincent Hall 570The RogersRamanujan identities a historical view Dennis Stanton, UMN Abstract:I will survey proofs of these identities, starting with Rogers in 1894. Included are excursions into qseries, partitions, combinatorics, Lie algebras, symmetric functions, statistical mechanics, probability and finite fields. I shall conclude with recent refinements in joint work with O'Hara. 
Fri Oct 05 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Oct 05 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Oct 05 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Oct 05 
Probability Seminar9:30am CANCELLED 
Thu Oct 04 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Oct 04 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Oct 04 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Stability of Ricci solitons Huaidong Cao  Ordway Visitor, Lehigh University Abstract:In this talk we continue our discussion of the previous week on stability of 
Thu Oct 04 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Oct 04 
Special Events and Seminars1:25pm  Vincent Hall 313The LanglandsKottwitzScholze method for Shimura varieties of abelian type Alex Youcis, University of California, Berkeley Abstract:The local (and global) Langlands conjectures attempt to bridge the major areas of harmonic analysis and number theory by forming a correspondence between representations which naturally appear in both areas. A key insight due to Langlands and Kottwitz is that one could attempt to understand such a conjectural correspondence by comparing the traces of natural operators on both sides of the bridge. Moreover, it was realized that Shimura varieties present a natural means of doing this. For global applications, questions of reduction type (at a particular prime p) for these Shimura varieties can often be avoided, and for this reason the methods of Langlands and Kottwitz focused largely on the setting of good reduction. But, for local applications dealing with the case of bad reduction is key. The setting of bad reduction was first dealt with, for some simple Shimura varieties, by Harris and Taylor which they used, together with the work of many other mathematicians, to prove the local Langlands conjecture for GL_n. A decade later Scholze gave an alternative, more geometric, way to understand the case of bad reduction for certain Shimura varieties and was able to reprove the local Langlands conjecture for GL_n. In this talk we will discuss an extension of the ideas of Scholze to a wider class of Shimura varieties, as well as the intended application of these ideas to the local Langlands conjectures for more general groups. 
Thu Oct 04 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Oct 04 
Student Number Theory Seminar12:20pm  Vincent Hall 313Student Number Theory 
Thu Oct 04 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Oct 03 
PDE Seminar3:30pm  Vincent Hall 570PDE Seminar 
Tue Oct 02 
Ordway Lecture Series2:30pm  Vincent Hall 16Microlocal codimensionthree conjecture Kari Vilonen, University of Melbourne, Ordway Visitor Abstract:Special functions (or distributions) can be understood and analyzed in terms of the systems of differential equations they satisfy. To this end, a general theory of systems of linear (micro) differential equations was developed by the Sato school in Kyoto. This point of view, in its various incarnations, is now ubiquitous in many parts of mathematics. For example, in the geometric Langlands program and representation theory it allows us to replace functions and group representations by geometric objects, perverse sheaves or Dmodules. It has been wellknown for a long time that the description of these objects gains more symmetry when one passes to the cotangent bundle. We explain the shape of the general microlocal structure of these objects and discuss, in particular, the role played by the codimensionthree conjecture which was proved by Masaki Kashiwara and the speaker a few years ago. 
Tue Oct 02 
Dynamical Systems2:30pm  Ford Hall 130Dynamical Systems Seminar 
Tue Oct 02 
Math Physics Seminar12:20pm  Vincent Hall 313Math Physics Seminar 
Tue Oct 02 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Oct 02 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Oct 01 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1LaxPhillips in rationalrank one Paul Garrett 
Mon Oct 01 
Applied and Computational Math Colloquium3:35pm  Vincent Hall 207Applied and Computational Math Colloquium 
Mon Oct 01 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: GrothendieckTeichmuller group and braided Hopf algebras Craig Westerland, University of Minnesota Abstract:The primitives in a classical Hopf algebra form a Lie algebra (in fact, a Lie subalgebra of the Hopf algebra). For a braided Hopf algebra, this is no longer the case. Consequently, all of the structure theorems for Hopf algebras (e.g., the MilnorMoore and PoincaréBirkhoffWitt theorems) break down in this setting. This is a report on ongoing work in which we construct an operad (a braided form of the Lie operad) which governs the algebraic structure of the primitives in a braided Hopf algebra. We can interpret this operad in terms of the homology of covering spaces of the 2dimensional little disks operad. This gives rise to an action of Drinfeld's GrothendieckTeichmuller group on this operad which may be related to Drinfeld's original definition of this group. 
Mon Oct 01 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Mon Oct 01 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Tyler Whitehouse, Gigantum 
Mon Oct 01 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Sep 28 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar  No Seminar 
Fri Sep 28 
Combinatorics Seminar3:35pm  Vincent Hall 570Pattern inventory polynomials for consonances and dissonances Octavio AgustínAquino, Universidad Tecnológica de la Mixteca Abstract:Dennis White obtained formulas from the PólyaRedfield theory for counting patterns with a certain group of automorphisms. We apply this to the problem of counting the socalled strong dichotomies, which are selfcomplementary rigid patterns of equitempered scales with an even number of tones. Strong dichotomies are models for the selection of consonances and dissonances in counterpoint, and are of capital importance for Guerino Mazzola's counterpoint theory. Furthermore, pattern inventory polynomials for strong dichotomies exhibit, in certain cases, a kind of cyclic sieving phenomenon, and we conjecture that there is a nice regularity for the cases when this holds true. 
Fri Sep 28 
Probability Seminar2:30pm  Vincent Hall 209Stationary coalescing walks on the lattice Arjun Krishnan, University of Rochester Abstract:Consider a measurable dense family of semiinfinite nearestneighbor paths on the integer lattice in d dimensions. If the measure on the paths is translation invariant, we completely classify their collective behavior in d=2 under mild assumptions. We use our theory to classify the behavior of semiinfinite geodesics in random translation invariant metrics on the lattice; it applies, in particular, to first and lastpassage percolation. We also construct several examples displaying unexpected behaviors. (joint work with Jon Chaika) 
Fri Sep 28 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Sep 28 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Sep 28 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305If a tree falls in the woods and nobody hears, does it make a sound? (Or, making sure your code runs anywhere.) Tyler Whitehouse, Gigantum Abstract:Most researchers dont have the time or the skill to apply the kinds of software development best practices needed to make their computational work transparent, reproducible, and easy to use. Despite repeated calls by publishers and funders to include usable and understandable code with publications, it is still too much work to be done with the resources allotted. Such problems are not unique to academia, and the penetration of machine learning and data science in industry has brought these issues to the attention of commercial enterprise as well. Reproducibility is a problem for everyone. This talk will demonstrate an open source data science platform that automates the issues around transparency, reproducibility, and ease of use for work done in open source languages and frameworks like Python and R. It will show how easy it is to set up computational and data science environments of varying complexity that can be shared with anybody in the world with no extra labor or set up. Bio 
Fri Sep 28 
Probability Seminar9:30am CANCELLED 
Thu Sep 27 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Sep 27 
Analysis and PDE Working Seminar3:40pm  Ford Hall 155Mean Field Games Sam Stewart Abstract:Finding emergent equilibria of games with finitely many players is hard, especially if players' strategies depend on each other. For example, what is the best strategy to escape a crowded room? Each player has to mentally simulate the potential strategies of other players so best strategies become recursive. Lasry and Lions (Pierre Lions is a Fields medalist for other work) devised a framework (mean field games) in 2007 for connecting these games to PDEs. The idea is simple: take the number of players to infinity and instead track a density and its velocity (strategy) field. Two coupled PDEs emerge, one in forward time (describing the world evolution) in one in backward time describing the best strategies. In this talk, I'll give a brief intro and then outline a cool example: crowd waves in soccer stadiums. A deadsimple mean field game model predicts traveling waves as long as the stadium's diameter isn't too small. 
Thu Sep 27 
Colloquium3:35pm  Vincent Hall 16Colloquium Abstract:Speaker: 
Thu Sep 27 
Ordway Lecture Series3:35pm  Vincent Hall 16Microlocal codimensionthree conjecture Kari Vilonen, University of Melbourne, Ordway Visitor Abstract:Special functions (or distributions) can be understood and analyzed in terms of the systems of differential equations they satisfy. To this end, a general theory of systems of linear (micro) differential equations was developed by the Sato school in Kyoto. This point of view, in its various incarnations, is now ubiquitous in many parts of mathematics. For example, in the geometric Langlands program and representation theory it allows us to replace functions and group representations by geometric objects, perverse sheaves or Dmodules. It has been wellknown for a long time that the description of these objects gains more symmetry when one passes to the cotangent bundle. We explain the shape of the general microlocal structure of these objects and discuss, in particular, the role played by the codimensionthree conjecture which was proved by Masaki Kashiwara and the speaker a few years ago. 
Thu Sep 27 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Second variation of Perelman's entropy and stability of Ricci solitons Huaidong Cao, Ordway Visitor, Lehigh University Abstract:Einstein metrics are critical points of the wellknown classical Hilbert action 
Thu Sep 27 
Commutative Algebra Seminar1:25pm  Ford Hall 170Commutative Algebra Seminar 
Thu Sep 27 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Sep 27 
Student Number Theory Seminar12:20pm  Vincent Hall 313Student Number Theory 
Thu Sep 27 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Sep 26 
PDE Seminar3:30pm  Vincent Hall 570PDE Seminar 
Tue Sep 25 
Colloquium3:35pm  Vincent Hall 16Microlocal codimensionthree conjecture Kari Vilonen, University of Melbourne, Ordway Visitor Abstract:Special functions (or distributions) can be understood and analyzed in terms of the systems of differential equations they satisfy. To this end, a general theory of systems of linear (micro) differential equations was developed by the Sato school in Kyoto. This point of view, in its various incarnations, is now ubiquitous in many parts of mathematics. For example, in the geometric Langlands program and representation theory it allows us to replace functions and group representations by geometric objects, perverse sheaves or Dmodules. It has been wellknown for a long time that the description of these objects gains more symmetry when one passes to the cotangent bundle. We explain the shape of the general microlocal structure of these objects and discuss, in particular, the role played by the codimensionthree conjecture which was proved by Masaki Kashiwara and the speaker a few years ago. 
Tue Sep 25 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Sep 25 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Sep 24 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1LaxPhillips estimates [cont'd] Paul Garrett 
Mon Sep 24 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 24 
Dynamical Systems2:30pm  Vinent Hall 570Water transport in models of dryland vegetation patterns Punit Gandhi, MBI, OhioState University Abstract:Regular spatial patterns in the vegetation growth of dryland ecosystems are thought to arise through selforganization in response to water scarcity. This behavior has been qualitatively reproduced by reactionadvectiondiffusion systems that model various interactions between the plants and their environment. The patterns most often appear on very gentle slopes as bands of vegetation separated by bare soil with characteristic spacing on the order of 100 meters. I will use a simple modeling framework and an idealized topography to discuss the role of water transport in determining (1) the shape of individual vegetation bands and (2) the region of the landscape occupied vegetation patterns. The results are in qualitative agreement with observations from remote sensing data, and suggest that the placement of the patterns relative to ridges and valleys on the terrain may provide some indication of resilience to ecosystem collapse under aridity stress. I will also discuss prospects for improved water transport models that provide a more detailed picture of processes governing surface/subsurface water dynamics across timescales. 
Mon Sep 24 
IMA Data Science Lab Seminar1:25pm  Lind 305Genetics of mRNA and Protein Expression in Large Yeast Populations Frank Albert, University of Minnesota, Twin Cities Abstract:Genetic variation among individuals is an important source of phenotypic variation within species. Many of these genetic effects are due to regulatory variation that influences gene expression. However, the full extent and nature of regulatory variation remains unknown due to the limited sample sizes that are typically studied, resulting in low statistical power. I will discuss our ongoing work addressing this limitation for the proteome and the transcriptome in the yeast Saccharomyces cerevisiae. For protein levels, we devised an approach based on extremely large pools of genetically different cells that carry proteins with fluorescent tags. For mRNA levels, we used RNA sequencing to profile gene expression in more than 1,000 recombinant yeast individuals. The statistical power of this dataset is high enough to map thousands of regulatory loci that together account for >70% of the heritability of mRNA levels. Together, these data provide a comprehensive view of how genetic variation influences gene expression. 
Mon Sep 24 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Sep 21 
MCFAM Seminar5:30pm  Vincent Hall 16Topological Data applied to Finance Kaisa Taipale  2018 MCFAM Summer Seminar Students, University of Minnesota 
Fri Sep 21 
Combinatorics Seminar3:35pm  Vincent Hall 570Science Fiction 2018 Adriano Garsia, UC San Diego Abstract:http://wwwusers.math.umn.edu/~hopki319/seminar_fall18.html#20180921 
Fri Sep 21 
Probability Seminar2:30pm  Vincent Hall 209The maximum of the characteristic polynomial for a random permutation matrix Nicholas Cook, UCLA Abstract:Let $P$ be a uniform random permutation matrix of size $N$ and let $\chi_N(z)= \det(zI  P)$ denote its characteristic polynomial. We prove a law of large numbers for the maximum modulus of $\chi_N$ on the unit circle, specifically, 
Fri Sep 21 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Sep 21 
Student Topology Seminar1:30pm  Vincent Hall 311Student Algebra and Topology Seminar 
Fri Sep 21 
Probability Seminar9:30am CANCELLED 
Thu Sep 20 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Sep 20 
Colloquium3:35pm  Vincent Hall 16Colloquium 
Thu Sep 20 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Monotonicity formulas and Type I singularities Huaidong Cao, Ordway Visitor, Lehigh University Abstract:In this talk we shall introduce Huisken's monotonicity formula for the mean curvature flow and Perelman's monotonicity formulas for the Ricci flow. We shall discuss their applications, including the role they play in studying TypeI singularities of the flows. 
Thu Sep 20 
Commutative Algebra Seminar1:25pm  Ford Hall 170Random Monomial Ideals Jay Yang, University of Minnesota Abstract:I will discuss the contents of my joint paper with Daniel Erman, Random Flag Complexes and Asymptotic Syzygies. In this paper we use the StanleyReisner ideals of random flag complexes to construct new examples of Ein and Lazarsfeld's nonvanishing for asymptotic syzygies, and of Ein, Erman, and Lazarsfeld's conjecture on the asymptotic normal distribution of Betti numbers. I will also discuss some work in progress related to the Random Monomial Ideals paper by De Loera, Petrovic, Silverstein, Stasi, and Wilburne. 
Thu Sep 20 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Sep 20 
Student Number Theory Seminar12:20pm  Vincent Hall 313Student Number Theory 
Thu Sep 20 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Sep 19 
PDE Seminar3:30pm  Vincent Hall 570On sparse bounds for some biparameter operators Jose Conde Alonso, Department of Mathematics, Brown University Abstract:The last few years have seen a great deal of work around the concept of sparse domination. This is a technique that allows one to study quantitative inequalities for a wide range of important operators in harmonic analysis in a unified and precise way. We briefly review what sparse domination is and we will explain the very different situation that one en counters when the operators under study are biparametric, that is, when we consider spaces whose dilations need not be isotropic. Based on joint work (in progress) with Alex Barron, Yumeng Ou and Guillermo Rey. 
Tue Sep 18 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Tue Sep 18 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Sep 17 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1LaxPhillips estimates for rankone groups Paul Garrett, University of Minnesota 
Mon Sep 17 
Topology Seminar3:30pm  Vincent Hall 301Topology Seminar: TBA 
Mon Sep 17 
Dynamical Systems2:30pm  Vinent Hall 570Careful or colorful: A mathematical model for the evolution of animal ornaments Danny Abrams, Northwestern Abstract:Extravagant and costly ornaments (e.g., deer antlers or peacock feathers) are found throughout the animal kingdom. Charles Darwin was the first to suggest that female courtship preferences drive ornament development through sexual selection. In this talk I will describe a minimal mathematical model for the evolution of animal ornaments, and will show that even a greatly simplified model makes nontrivial predictions for the types of ornaments we expect to find in nature. 
Mon Sep 17 
Cockburn's Seminar9:00am  Vincent Hall 301Cockburn's Seminar 
Fri Sep 14 
MCFAM Seminar5:30pm  Vincent Hall 16How to Get the Most Out of the MFM MFM 2nd Yr. Student/Alumni Panel, U of M  School of Mathematics  MCFAM 
Fri Sep 14 
Combinatorics Seminar3:35pm  Vincent Hall 570Ehrhart polynomial of a polytope plus dilating zonotope Sam Hopkins, University of Minnesota Abstract:In earlier joint work with Pavel Galashin, Thomas McConville, and Alex Postnikov, we introduced certain directed graphs, depending on a deformation parameter k, whose vertex sets are the weight lattice of a root system. We showed that there is a natural way to label the connected components of these directed graphs across values of k so that the number of points in each connected component is a polynomial in k, which we termed an "Ehrhartlike polynomial" in analogy with the Ehrhart polynomials of lattice polytopes. We conjectured that these Ehrhartlike polynomials have nonnegative integer coefficients. This conjecture prompts us to study the polynomial which counts the number of lattice points in the Minkowski sum of a permutohedron and a dilating regular permutohedron, or more generally in the Minkowski sum of a polytope and a dilating zonotope. We extend Stanley's wellknown formula for the Ehrhart polynomial of a zonotope to give a formula for this polynomial. And we then use this formula, together with a subtle integrality property of slices of permutohedra, to give a positive, combinatorial formula for the Ehrhartlike polynomials mentioned above. This is joint work with Alex Postnikov. 
Fri Sep 14 
Probability Seminar2:30pm  Vincent Hall 209The travel time to infinity in percolation WaiKit Lam, UMN Abstract:On the twodimensional square lattice, assign i.i.d. nonnegative weights to the edges with common distribution $F$. For which distributions $F$ is there an infinite selfavoiding path with finite total weight? It has long been known that there is no such infinite path when $F(0) < 1/2$ (there are only finite clusters of zeroweight edges), and there is one when $F(0) > 1/2$ (there is an infinite cluster of zeroweight edges). The critical case, $F(0) = 1/2$, is considerably more difficult due to the presence of finite clusters of zeroweight edges on all scales. In a joint work with M. Damron and X. Wang, we give a necessary and sufficient condition on $F$ for the existence of an infinite finiteweight path, and study the asymptotic behaviors of the firstpassage time in the critical case. I will also discuss a recent work with M. Damron and J. Hanson in which we prove some limit theorems for the firstpassage time in the critical case on the triangular lattice. 
Fri Sep 14 
Lie Theory Seminar2:30pm  Vincent Hall 313Dmodules, perverse sheaves, and the RiemannHilbert correspondence: an overview KaiWen Lan, University of Minnesota 
Fri Sep 14 
Student Topology Seminar1:30pm  Vincent Hall 311FominKirillov Algebras, and why we care Greg Michel Abstract:In this talk, I'll introduce an interesting family of algebras called the FominKirillov algebras. We'll explore some basic properties and talk about how better understanding these algebras could lead to some fascinating results in Algebraic Topology. 
Fri Sep 14 
Probability Seminar9:30am CANCELLED 
Thu Sep 13 
Student Combinatorics Seminar4:40pm  Vincent Hall 570Student Combinatorics and Algebra Seminar 
Thu Sep 13 
Colloquium3:35pm  Vincent Hall 16Singularities of the Ricci flow and Ricci solitons HuaiDong Cao, Lehigh University, Ordway Visitor Abstract:Understanding formation of singularities has been an important subject in the study of the Ricci flow and other geometric flows. It turns out generic singularities in the Ricci flow are modeled on shrinking Ricci solitons. In this talk, I will discuss some of the recent progress on classifications of shrinking Ricci solitons and their stability/instability with respect to Perelman's $\nu$entropy. 
Thu Sep 13 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Sep 13 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Sep 13 
Student Number Theory Seminar12:20pm  Vincent Hall 313Student Number Theory 
Thu Sep 13 
Climate Seminar11:15am  Vincent Hall 570Climate Seminar 
Wed Sep 12 
PDE Seminar3:30pm  Vincent Hall 570Estimates of the entropy numbers of the Sobolev embedding near the limit case Yuri Netrusov, Bristol Abstract:In 1967 M.Birman and M.Solomyak proved the following remarkable result. Let l,d be positive integers in [1,\infty], and T be the embedding of W^l_p((0,1)^d) to L^q ((0,1)^d). Suppose that 0 < 1/p1/q < l/d. 
Tue Sep 11 
Climate Seminar11:15am  Vincent Hall 570The Scientific Case for Anthropogenic Warming Richard McGehee, University of Minnesota 
Tue Sep 11 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Sep 10 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 1Automorphic Forms and Number Theory 
Mon Sep 10 
Dynamical Systems2:30pm  Vinent Hall 570Dynamical Systems Seminar 
Fri Sep 07 
MCFAM Seminar5:30pm  Vincent Hall 16MCFAM Seminar 
Fri Sep 07 
Analysis and PDE Working Seminar3:35pm  Vincent Hall 206Sufficient conditions for $C^{1,\alpha}$ parametrization and rectifiability Silvia Ghinassi, Stony Brook University Abstract:We provide sufficient conditions for a set or measure in $\mathbb{R}^n$ to be $C^{1,\alpha}$ $d$rectifiable, with $\alpha \in [0,1]$. The conditions use a BishopJones type square function and all statements are quantitative in that the $C^{1,\alpha}$ constants depend on such a function. Key tools for the proof come from Guy David and Tatiana Toro's parametrization of Reifenberg flat sets (with holes) in the H\"{o}lder and Lipschitz categories. 
Fri Sep 07 
Probability Seminar2:30pm  Vincent Hall 209Probability Seminar 
Fri Sep 07 
Lie Theory Seminar2:30pm  Vincent Hall 313Lie Theory Seminar 
Fri Sep 07 
Probability Seminar9:30am CANCELLED 
Thu Sep 06 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570Differential Geometry / Symplectic Topology Seminar 
Thu Sep 06 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu Sep 06 
Student Number Theory Seminar12:20pm  Vincent Hall 313Student Number Theory 
Thu Sep 06 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Wed Sep 05 
Commutative Algebra Seminar10:10am  Vincent Hall 313Using mixed GaussManin systems to project, restrict, and dualize $A$hypergeometric systems Avi Steiner, Purdue Abstract:Let $A$ be an integer matrix, and assume that its semigroup ring $\mathbb{C}[\mathbb{N} A]$ is normal. I will discuss how to use mixed and dual mixed GaussManin systems, a notion I introduced recently, to compute the holonomic dual of an $A$hypergeometric system; and to compute, for $F$ a face of the cone of $A$, the projection and restriction of an $A$hypergeometric system to the coordinate subspace corresponding to $F$. 
Tue Sep 04 
Climate Seminar11:15am  Vincent Hall 570Climate Change Seminar 
Tue Sep 04 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Aug 31 
Probability Seminar9:30am CANCELLED 
Tue Aug 28 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Aug 27 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Aug 24 
Probability Seminar9:30am CANCELLED 
Wed Aug 22 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Aug 21 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Aug 20 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Aug 17 
Probability Seminar9:30am CANCELLED 
Wed Aug 15 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Aug 14 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Aug 13 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Aug 10 
Probability Seminar9:30am CANCELLED 
Wed Aug 08 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Aug 07 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Aug 06 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Aug 03 
Combinatorics Seminar1:30pm  Vincent Hall 113Combinatorics Seminar Theo Douvropoulos, IRIF, University of ParisDiderot 
Fri Aug 03 
Probability Seminar9:30am CANCELLED 
Thu Aug 02 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Thu Aug 02 
Combinatorics Seminar11:00am  Vincent Hall 570Combinatorics Seminar Jang Soo Kim, Sungkyunkwan University Abstract:We introduce lecture hall tableaux, which are fillings of a skew Young diagram satisfying certain conditions. Lecture hall tableaux generalize both lecture hall partitions and antilecture hall compositions, and also contain reverse semistandard Young tableaux as a limit case. We show that the coefficients in the Schur expansion of multivariate little $q$Jacobi polynomials are generating functions for lecture hall tableaux. Using a Selbergtype integral we show that the moment of multivariate little $q$Jacobi polynomials, which is equal to a generating function for lecture hall tableaux of a Young diagram, has a product formula. We also explore various combinatorial properties of lecture hall tableaux. This is joint work with Sylvie Corteel. 
Wed Aug 01 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Wed Aug 01 
Special Events and Seminars10:00am  Vincent Hall 16REU Final Presentations 
Tue Jul 31 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Tue Jul 31 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Jul 31 
Special Events and Seminars10:00am  Vincent Hall 16REU Final Presentations 
Mon Jul 30 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Jul 30 
Special Events and Seminars10:00am  Vincent Hall 16REU Final Presentations 
Fri Jul 27 
Probability Seminar9:30am CANCELLED 
Thu Jul 26 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Thu Jul 26 
Combinatorics Seminar11:00am  Vincent Hall 570Noncrossing partitions, the Bruhat order, and the cluster complex (joint work with Philippe Biane) Matthieu JosuatVerges, University of ParisEast MarnelaVallee, CNRS Abstract:Noncrossing partitions of a real reflection group can be defined as an interval in the absolute order (itself being defined using the reflection length). An observation at the origin of this work is the following: a cover relation in noncrossing partitions give two elements that are comparable in the Bruhat order, but the two orders might agree or disagree on such a pair. This leads to distinguishing two kinds of cover relations in noncrossing partitions, hence two new orders. We study various enumerative properties of these, that leads to nice connection with the cluster complex. 
Wed Jul 25 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Jul 24 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Tue Jul 24 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Jul 23 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Jul 20 
Probability Seminar9:30am CANCELLED 
Thu Jul 19 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Wed Jul 18 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Jul 17 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Tue Jul 17 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Jul 16 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Jul 13 
Probability Seminar9:30am CANCELLED 
Thu Jul 12 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Wed Jul 11 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Jul 10 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Tue Jul 10 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Jul 09 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Jul 06 
Probability Seminar9:30am CANCELLED 
Thu Jul 05 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Wed Jul 04 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Jul 03 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Tue Jul 03 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Jul 02 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Jun 29 
Probability Seminar9:30am CANCELLED 
Thu Jun 28 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Wed Jun 27 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Jun 26 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Tue Jun 26 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Jun 25 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Jun 22 
Probability Seminar9:30am CANCELLED 
Thu Jun 21 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Wed Jun 20 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Jun 19 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Tue Jun 19 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Jun 18 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Jun 15 
Probability Seminar9:30am CANCELLED 
Thu Jun 14 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Wed Jun 13 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Jun 12 
Special Events and Seminars3:00pm  Vincent Hall 301Representation Theory Seminar TBA 
Tue Jun 12 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Jun 11 
Combinatorics Seminar3:30pm  Vincent Hall 206Wildly Nontransitive Dice Joe Buhler Abstract:Nontransitive triples of dice have been known for (at least) 60 years. Let A = {2,6,7}, B = {1,5,9}, C = {3,4,8} denote dice taking each of the three indicated values with probability 1/3. As you can (and should!) check, A dominates B in the sense that when each is rolled the probability that A > B is greater than 1/2. Moreover, B dominates C, and C dominates A, so the dominance relation is nontransitive. To make matters worse, the triple A[2], B[2], C[2]  where A[2] denotes the sum of two rolls of A, etc.  is (as you have perhaps already checked) also a nontransitive triple. However, the cyclic dominance order is exactly the reverse of the earlier one. The goal of this talk is to present sets of dice with vastly more peculiar nontransitivity properties. 
Mon Jun 11 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Jun 08 
Probability Seminar9:30am CANCELLED 
Wed Jun 06 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue Jun 05 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon Jun 04 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri Jun 01 
Probability Seminar9:30am CANCELLED 
Wed May 30 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue May 29 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon May 28 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri May 25 
Probability Seminar9:30am CANCELLED 
Wed May 23 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue May 22 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon May 21 
Climate Seminar1:25pm  570 Vincent HallClimate Change Seminar Richard McGehee 
Fri May 18 
Probability Seminar9:30am CANCELLED 
Tue May 15 
Topology Seminar2:30pm  Vincent Hall 2Topology Seminar 
Tue May 15 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Mon May 14 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 364Automorphic Forms and Number Theory 
Mon May 14 
Topology Seminar1:30pm  Vincent Hall 209Topology Seminar 
Fri May 11 
Lie Theory Seminar3:30pm  Vincent 364Lie Theory Seminar 
Fri May 11 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar 
Fri May 11 
Probability Seminar9:30am CANCELLED 
Thu May 10 
Student Combinatorics Seminar4:30pm  Vincent Hall 301Student Combinatorics Seminar 
Thu May 10 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Wed May 09 
Algebraic Representation Theory Seminar2:30pm  Vincent Hall 6Topological categories containing the category FI  continuation Cihan Bahran, University of Minnesota Abstract:This talk will not depend on any of the previous talks about the local cohomology of FImodules. One of the flagship applications of FImodules is on configuration spaces. In several cases, the natural FIaction on PConf(X) extends to an action of a topological category which FI strictly embeds into. The very presence of such an extended action significantly simplifies the associated sequence of representations of symmetric groups on cohomology, and in particular improves the stable ranges. 
Tue May 08 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue May 08 
Colloquium2:30pm  Vincent Hall 16Colloquium 
Tue May 08 
Topology Seminar2:30pm  Vincent Hall 2Topology Seminar 
Tue May 08 
Special Events and Seminars2:30pm  Ford Hall 130Undergraduate Mathematics Research Seminar 
Tue May 08 
Math Physics Seminar1:25pm  Vincent Hall 301Math Physics Seminar 
Tue May 08 
IMA Data Science Lab Seminar1:25pm  Lind 409Objective functionals of machine learning on graphs and their continuum limits Dejan Slepcev, Carnegie Mellon University Abstract:We will discuss variational problems arising in machine learning and their limits as the number of data points goes to infinity. Consider point clouds obtained as random samples of an underlying "groundtruth" measure. Graph representing the point cloud is obtained by assigning weights to edges based on the distance between the points. Many machine learning tasks, such as clustering and semisupervised learning, can be posed as minimizing functionals on such graphs. We consider functionals involving graph cuts, graph laplacians and their limits as the number of data points goes to infinity. We will discuss the limits of functionals when the number of data points goes to infinity. In particular we establish under what conditions the minimizers of discrete problems have a well defined continuum limit. 
Tue May 08 
Climate Seminar11:15am  570 Vincent HallClimate Change Seminar Richard McGehee 
Tue May 08 
Student Number Theory Seminar11:15am  Vincent Hall 313Student Number Theory Seminar 
Tue May 08 
Reading Seminar on Automorphic Forms10:00am  Vincent Hall 364Reading Seminar on Automorphic Forms 
Mon May 07 
Automorphic Forms and Number Theory3:35pm  Vincent Hall 364Automorphic Forms and Number Theory 
Mon May 07 
Cockburn's Seminar3:30pm  Ford Hall B10Cockburn's Seminar 
Mon May 07 
Special Events and Seminars2:30pm  Vincent Hall 20Dnamical Systems Seminar 
Mon May 07 
Topology Seminar1:30pm  Vincent Hall 209Topology Seminar 
Fri May 04 
MCFAM Seminar4:30pm  Vincent Hall 16MCFAM Seminar 
Fri May 04 
Combinatorics Seminar3:35pm  Vincent Hall 570GaleRobinson quivers, representations, and combinatorial formulas Max Glick, Ohio State Abstract:GaleRobinson sequences were one of the first examples of the Laurent phenomenon. Moreover, the associated quivers relate to the dimer model from physics. We investigate a family of representations of these quivers that are geared towards providing concrete information about the corresponding cluster algebras. In this way, we provide a representation theoretic explanation for known combinatorial formulas for the GaleRobinson sequence and also obtain similar formulas for several other cluster variables. This is joint work with Jerzy Weyman. 
Fri May 04 
Lie Theory Seminar3:30pm  Vincent 364Lie Theory Seminar 
Fri May 04 
Probability Seminar2:30pm  Vincent Hall 311Probability Seminar 
Fri May 04 
IMA/MCIM Industrial Problems Seminar1:25pm  Lind 305Lecture Tatiana Yarmola, J.P. Morgan AG 
Fri May 04 
Commutative Algebra Seminar12:20pm  Vincent Hall 209Commutative Algebra 
Fri May 04 
MathCEP Seminar11:15am  Vincent Hall 113MathCEP Seminar 
Fri May 04 
Probability Seminar9:30am CANCELLED 
Thu May 03 
Student Combinatorics Seminar4:30pm  Vincent Hall 301Student Combinatorics Seminar 
Thu May 03 
Colloquium3:30pm  Vincent Hall 16Fractal solutions of dispersive PDE on the torus Burak Erdogan, Department of Mathematics, University of Illinois Abstract:In this talk we discuss qualitative behavior of certain solutions to linear and nonlinear dispersive partial differential equations such as Schrodinger and Kortewegde Vries equations. In particular, we will present results on the fractal dimension of the solution graph and the dependence of solution profile on the algebraic properties of time. 
Thu May 03 
Differential Geometry and Symplectic Topology Seminar1:25pm  Vincent Hall 570BochnerKahler metrics (after R. Bryant) Rui Loja Fernandes  Ordway Visitor, UIUC Abstract:In a seminal paper, R. Bryant gave a local description of BochnerKahler metrics and a classification of germs of such metrics. In this talk I will sketch a new approach to this classification using the theory of integrability of Lie algebroids. It provides new insight and allows for more precise results, extending the work of Bryant. Our approach can also be used to solve other geometric classification problems (e.g., symplectic connections with special holonomy). This is ongoing joint work with Ivan Struchiner (U Sao Paulo, Brazil). 
Thu May 03 
Math Club Seminar12:20pm  Vincent Hall 570Math Club Seminar 
Thu May 03 
Ordway Lecture Series10:10am  Vincent Hall 16padic Hodge theory and homotopy theory Bhargav Bhatt, University of Michigan  Ann Arbor Abstract:In my colloquium talk on 4/26, I discussed the following result, giving a weak analogue of Hodge theory with torsion coefficients: if a smooth and proper complex variety X specializes to a smooth and proper variety X_p in characteristic p, then the mod p singular cohomology of X is controlled by the de Rham cohomology of X_p. The key innovation of this work is the construction of a padic cohomology theory that interpolates between known cohomology theories in padic geometry (such as padic etale cohomology and de Rham cohomology). In this talk, I shall discuss this construction and explain why it is closely related to certain periodicity theorems (such as Bott's and Bokstedt's) in homotopy theory. Joint work with Matthew Morrow and Peter Scholze. 
Thu May 03 
Geometric Analysis Learning Seminar10:00am  Vincent Hall 570Geometric Analysis Learning Seminar 
Wed May 02 
PDE Seminar3:35pm  Vincent Hall 570A Phase Field Model for Thin Elastic Structures with Topological Constraint Patrick Dondl, University of Freiburg, Germany Abstract:With applications in the area of biological membranes in mind, we consider the problem of minimizing Willmores energy among the class of closed, connected surfaces with given surface area that are confined to a fixed container. Based on a phase field model for Willmores energy originally introduced by de Giorgi, we develop a technique to incorporate the connectedness constraint into a diffuse interface model of elastic membranes. Our approach uses a geodesic distance function associated to the phase field to discern different connected components of the support of the limiting mass measure. We obtain both a suitable compactness property for finite energy sequences as well as a Gammaconvergence result. Furthermore, we present computational evidence for the effectiveness of our technique. The main argument in our proof is based on a new, natural notion to describe convergence of phase fields. 
Wed May 02 
Algebraic Geometry3:35pm  Vincent Hall 301Algebraic Geometry Seminar 
Wed May 02 
Algebraic Representation Theory Seminar2:30pm  Vincent Hall 6Algebraic Representation Theory Seminar 
Tue May 01 
Colloquium3:30pm  Vincent Hall 16Colloquium 
Tue May 01 
Colloquium2:30pm  Vincent Hall 16Colloquium 
Tue May 01 
Topology Seminar2:30pm  Vincent Hall 2Edge stabilization in the homology of graph braid groups Ben Knudsen, Harvard University Abstract:We discuss a novel type of stabilization map on the configuration spaces of a graph, which increases the number of particles occupying an edge. Through these maps, the homology of the configuration spaces forms a module over the polynomial ring generated by the edges of the graph, and we show that this module is finitely generated, implying eventual polynomial growth of Betti numbers over any field. Moreover, the action lifts to an action at the level of singular chains, which contains strictly more information; indeed, we show that this differential graded module is almost never formal over the ring of edges. These results, along with numerous calculations, arise from consideration of an explicit chain complex, which is a structured enhancement of a cellular model first considered by Swiatkowski. We arrive at this model through a localtoglobal approach combining ideas from factorization homology and discrete Morse theory. This is joint work with Byung Hee An and Gabriel DrummondCole. 
Tue May 01 
Special Events and Seminars2:30pm  Ford Hall 130Undergraduate Mathematics Research Seminar 
Tue May 01 
Math Physics Seminar1:25pm  Vincent Hall 301STEERING A PARTICLE ON A MATHEMATICALLY SMOOTH SURFACE Mike Hennessey, University of St. Thomas Abstract:We consider the general problem of steering an infinitesimal propelled and steerable particle traversing on a mathematically smooth (vs. frictionless) surface, analogous to propelled skiing on the slopes where both the speed and body yaw rate serve as inputs to the system and lateral motion is not allowed, i.e. through a no sideslip condition. Nonholonomic steering on the surface is a very interesting and challenging problem and several approaches are investigated: (1) steering using sinusoids (detailed), (2) steering on a trajectory, and (3) "driveandturn" (valid in this case). Prior to implementing the steering with sinusoids algorithm, it was necessary to transform the system into "onechained" form. The first step entailed conversion to an approximate onechained form model that possesses a certain structure, from which the process established by Murray et. al. can be successfully launched, where two special smooth scalar functions of the states are sought that possess special relationships to Lierelated distribution spaces associated with the control input vectors. Inputs are then transformed as well via specialized Lie derivatives. It was demonstrated through simulation that steering to an arbitrary system state on a faceted surface can be accomplished with sinusoidal inputs in only one maneuver set (i.e. maneuver A & B). Using this fact, the work presented culminates with steering to an arbitrary system state on a smooth surface that can be accomplished by essentially iterating on a steering algorithm that assumes the particle is on a plane tangent to the smooth surface at the point of interest. In this regard, it is shown that a sequence of maneuver sets (A_i, B_i) converges rather quickly in the example demonstrated. 
Tue May 01 
IMA Data Science Lab Seminar1:25pm  Lind 305Genetics of mRNA and protein expression in large yeast populations Frank Albert, University of Minnesota, Twin Cities Abstract:Genetic variation among individuals is an important source of phenotypic variation within species. Many of these genetic effects are due to regulatory variation that influences gene expression. However, the full extent and nature of regulatory variation remains unknown due to the limited sample sizes that are typically studied, resulting in low statistical power. I will discuss our ongoing work addressing this limitation for the proteome and the transcriptome in the yeast Saccharomyces cerevisiae. For protein levels, we devised an approach based on extremely large pools of genetically different cells that carry proteins with fluorescent tags. For mRNA levels, we used RNA sequencing to profile gene expression in more than 1,000 recombinant yeast individuals. The statistical power of this dataset is high enough to map thousands of regulatory loci that together account for >70% of the heritability of mRNA levels. Together, these data provide a comprehensive view of how genetic variation influences gene expression. 
Tue May 01 
IMA Data Science Lab Seminar1:25pm  Lind 305Lecture Zachi Attia, Mayo Clinic 