# Past Seminars

### Automorphic Forms & Number Theory [will not meet]

Automorphic Forms and Number Theory
Monday, February 27, 2017 - 3:35pm

### Cockburn's Seminar

Cockburn's Seminar
Monday, February 27, 2017 - 3:30pm

### State of Health Economy as we Transition to a new Administration

MCFAM Seminar
Dr. Stephen Parente, Associate Dean MBA Program and Specialty Masters Programs, Professor & Director, Medical Industry Leadership Institute
Friday, February 24, 2017 - 5:30pm
##### Abstract:

Professor Steve Parente will talk about the long arc of health reform in the United States and the choices that are now being considered for the the next chapter. He will present results for a health reform microsimulation model to highlight the results of those choices on the uninsured in the US, premiums paid and federal budget implications.

### Reading Seminar on Harmonic Analysis

Special Events and Seminars
Friday, February 24, 2017 - 3:35pm

### Set-Valued Skyline

Combinatorics Seminar
Cara Monical, UIUC
Friday, February 24, 2017 - 3:35pm
##### Abstract:

Set-valued tableaux play an important role in combinatorial K-theory. Separately, semistandard skyline fillings are a combinatorial model for Demazure atoms and key polynomials. We unify these two concepts by defining a set-valued extension of semistandard skyline fillings and then give analogues of results of J. Haglund, K. Luoto, S. Mason, and S. van Willigenberg.

### Applied and Computational Math Colloquium

Applied and Computational Math Colloquium
Friday, February 24, 2017 - 2:30pm

### The limiting density of the positive spins for majority dynamics on 3-regular tree has no jumps

Probability Seminar
Arnab Sen, UMN
Friday, February 24, 2017 - 2:30pm
##### Abstract:

We consider the majority dynamics on the infinite 3-regular tree, where each vertex has an i.i.d. Poisson clock attached to it, and when the clock of a vertex rings, the vertex looks at the spins of its three neighbors and flips its spin, if necessary, to come into agreement with majority of its neighbors. The initial spins of the vertices are taken to be i.i.d. Bernoulli random variables with parameter p. We show that the probability that the limiting spin at the root is + is continuous with respect to the initial bias p. Our argument relies upon mass transport principle. The talk is based on an ongoing work with M. Damron.

### Math Physics Seminar

Math Physics Seminar
Friday, February 24, 2017 - 1:25pm

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, February 23, 2017 - 4:30pm

### Colloquium

Colloquium
Thursday, February 23, 2017 - 2:30pm

### Lagrangian-type Submanifolds of G2 and Spin(7) Manifolds

Differential Geometry and Symplectic Topology Seminar
Rebecca Glover, University of St. Thomas
Thursday, February 23, 2017 - 1:25pm
##### Abstract:

The study of Lagrangian submanifolds has played a fundamental role in furthering the field of symplectic geometry. Lagrangian submanifolds reveal information about Hamiltonian mechanics, symplectic rigidity, and local invariants of symplectic manifolds. Further, a deeper understanding of Lagrangian submanifolds has provided insight towards establishing a correspondence between Calabi-Yau mirror pairs in Kontsevich's homological mirror symmetry via the Fukaya category. In this talk, we discuss the analogues for Lagrangian submanifolds in G2 and Spin(7) geometry. We will discuss properties of these submanifolds as well as their deformation spaces. This is joint work with Sema Salur.

### Student Number Theory Seminar

Student Number Theory Seminar
Thursday, February 23, 2017 - 12:20pm

### Welcome Week

Math Club Seminar
Thursday, February 23, 2017 - 12:20pm

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, February 23, 2017 - 11:15am

### Recursive Integral Eigenvalue Solver with Cayley Transformation

IMA Annual Program
Jiguang Sun, Michigan Technological University
Thursday, February 23, 2017 - 11:00am
##### Abstract:

Recently, a non-classical eigenvalue solver, called {\bf RIM}, was proposed to compute (all) eigenvalues in a region on the complex plane. Without solving any eigenvalue problems, it tests if a region contains eigenvalues using an approximate spectral projection. Regions that contain eigenvalues are subdivided and tested recursively until eigenvalues are isolated with a specified precision. This makes {\bf RIM} an eigenvalue solver distinct from all existing methods. Furthermore, it requires no a priori spectral information. In this talk, we implement an improved version of {\bf RIM} for non-Hermitian eigenvalue problems. Using Cayley transforms, the computation cost is reduced significantly also it inherits all the advantages of RIM. Numerical examples are presented and compared with 'eigs' in Matlab.

### Convexity of Level Sets and a Two-point Function

Geometric Analysis Learning Seminar
Thursday, February 23, 2017 - 10:00am

### Reading Seminar for Automorphic Forms

Thursday, February 23, 2017 - 8:00am

### A Free Boundary Problem on Cones

PDE Seminar
Wednesday, February 22, 2017 - 3:35pm
##### Abstract:

The one phase free boundary problem shares a well-known connection to area-minimizing surfaces. In this talk we review this connection and then discuss the one-phase problem on rough surfaces, and in particular cones. After reviewing results of the author with Chang Lara for the one-phase problem on two-dimensional cones, we revisit the connection to area-minimizing surfaces to gain insight into the problem on higher dimensional cones. We then present new results on when the free boundary is allowed to pass through the vertex of a three-dimensional cone as well as results for higher dimensional cones.

### Student Algebraic Topology Seminar

Special Events and Seminars
Wednesday, February 22, 2017 - 2:30pm

### Algebraic Geometry Seminar

Algebraic Geometry
Wednesday, February 22, 2017 - 2:30pm

### New methods in free boundary problems

Analysis and PDE Working Seminar
Wednesday, February 22, 2017 - 11:15am
##### Abstract:

In this talk we will give an introduction to the area of free boundary problems. We will discuss some of the inherent difficulties in studying free boundary problems. After reviewing classical techniques and their limitations, we will discuss new techniques that have emerged over the past couple of years (some in the past couple of months) to solve open problems. We will conclude by discussing various open problems and future directions in free boundary problems.

### Lie Theory Seminar

Lie Theory Seminar
Tuesday, February 21, 2017 - 3:35pm

### Analysis and PDE Working Seminar

Analysis and PDE Working Seminar
Tuesday, February 21, 2017 - 2:30pm

### Colloquium

Colloquium
Tuesday, February 21, 2017 - 2:30pm

### Colloquium

Colloquium
Tuesday, February 21, 2017 - 2:30pm

### Diferential Geometry and Symplectic Topology Seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, February 21, 2017 - 1:25pm

### “Big Data” in Image Analysis

IMA Data Science Lab Seminar
Thomas Pengo, University of Minnesota, Twin Cities
Tuesday, February 21, 2017 - 1:25pm
##### Abstract:

Image analysis is the quantitative analysis of images. It feeds on advances in mathematics, signal processing and machine learning to apply them to information extraction from images, N-dimensional sampled signals. In this talk we will attempt to explore applications of mathematics to different areas of image analysis, from acquisition, to processing, to data exploration. We will see how advances in sensing equipment creates additional challenges for processing and extracting scientific insights.

Thomas obtained his BSc and MSc in Computer Engineering at Politecnico di Milano in 2005. His PhD was defended in 2010 at the University of Navarra, with the title "Automation of Early Lung Cancer Detection", a work he developed at the Center for Applied Medical Research in Pamplona. During his Ph.D. he was a visiting scientist at the CBIA in Brno and at Sudar Lab in the Lawrence Berkeley National Laboratory. After a two years postdoc at the Ecole Polytechnique Federale de Lausanne working on the analysis of super-resolution microscopy images at the LEB he worked as an image analyst at the Center for Genomic Regulation in Barcelona in the Advanced Light Microscopy Unit and in the laboratory of Luis Serrano, before moving to the U of M.

### Climate Change Seminar - NOT MEETING

Climate Seminar
Tuesday, February 21, 2017 - 11:15am

### [will not meet]

Automorphic Forms and Number Theory
Monday, February 20, 2017 - 3:35pm

### Cockburn's Seminar

Cockburn's Seminar
Monday, February 20, 2017 - 3:30pm

### Wave phenomena in metamaterials and photonic crystals

Applied and Computational Math Colloquium
Robert Lipton, Louisiana State Univ.
Monday, February 20, 2017 - 2:30pm
##### Abstract:

Metamaterials are materials whose electromagnetic or acoustic
properties are controlled by their internal structure. Typically these
structures can be periodic and the period or characteristic length scale
of the internal structure is much smaller than the wavelength. A familiar
example is red stained glass made from sub wavelength gold nanoparticles.
On the other hand when the period of the internal structure is on the same
length scale as the wavelength then destructive interference can occur.
This gives rise to frequency intervals where no waves can propagate inside
the material. These are the well known photonic band gap crystals and
their effects can be seen in the coloration of butterfly wings. In this
lecture we provide a brief history of metamaterials and photonic band gap
crystals and provide an overview of the mathematical modeling. We
highlight auxiliary spectral problems directly related to the physical
structure of these materials. We illustrate how these spectra can be used
as tools in the design of both metamaterials and photonic band gap
crystals. This is joint work with Yue Chen and Robert Viator.

### Model Validation

MCFAM Seminar
Dr. James West, Federal Reserve Bank of Minneapolis
Friday, February 17, 2017 - 5:30pm
##### Abstract:

The presentation will focus on model validation’s role within a model risk management framework. Applications of model validation concepts to the loss forecasting methodologies and the CCAR exercise will be discussed.

### Lyashko-Looijenga Morphisms and Geometric Factorizations of a Coxeter Element

Combinatorics Seminar
Friday, February 17, 2017 - 3:35pm
##### Abstract:

A common theme in Combinatorics is an unconditional love for the symmetric group. We like to investigate structural and numerological properties of various objects associated with it. It often happens that such objects and phenomena can be generalized to the other (complex) reflection groups as well.

A problem that goes back to Hurwitz and the 19th century is to enumerate (reduced) factorizations of the long cycle (12..n)? Sn? into factors from prescribed conjugacy classes. In the reflection groups case, it corresponds to enumerating factorizations of a Coxeter element.

Bessis gave a beautiful geometric interpretation of such factorizations by using a variant of the Lyashko-Looijenga (LL) map, a finite morphism coming from Singularity theory. We extend some of Bessis' and Ripoll's work and use the LL map to enumerate the so called "primitive factorizations" of a Coxeter element c. That is, factorizations of the form c=w? t1? tk?, where w? belongs to a prescribed conjugacy class and the ti?'s are reflections.

### Reading Seminar on Harmonic Analysis

Special Events and Seminars
Friday, February 17, 2017 - 3:35pm

### Ground state energy and energy landscape of the spherical mixed p-spin model

Probability Seminar
Wei-Kuo Chen, UMN
Friday, February 17, 2017 - 2:30pm
##### Abstract:

Spin glasses are disordered spin systems originated from the desire of understanding the strange magnetic behavior of certain alloys in physics. In this talk, we will focus on the landscape of the spherical mixed p-spin model. First, we will present the Crisanti-Sommers formula for the ground state energy. Second, we will discuss some geometric properties of the energy landscape corresponding to different mixtures. Based on joint works with A. Auffinger and A. Sen.

### Applied and Computational Math Colloquium

Applied and Computational Math Colloquium
Friday, February 17, 2017 - 2:30pm

### 3-body problem: quantum ground state, classical planar dynamics

Math Physics Seminar
Sasha Turbiner, UNAM Mexico
Friday, February 17, 2017 - 1:25pm
##### Abstract:

The quantum and classical dynamics of a $3$-body system with equal masses
in $d$-dimensional space with interaction depending only on mutual
(relative) distances.

The study is restricted to solutions in the space of relative motion which
are functions of mutual (relative) distances only.

It is shown that these solutions correspond to motion of 3-dimensional
particle in curved space with remarkable metric. (Quasi)-exactly-solvable
Schroedinger operators in this curved space are found.

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, February 16, 2017 - 4:30pm

### Colloquium

Colloquium
Thursday, February 16, 2017 - 2:30pm

### Diferential Geometry and Symplectic Topology Seminar

Differential Geometry and Symplectic Topology Seminar
Thursday, February 16, 2017 - 1:25pm

### Student Number Theory Seminar

Student Number Theory Seminar
Thursday, February 16, 2017 - 12:20pm

### Welcome Week

Math Club Seminar
Thursday, February 16, 2017 - 12:20pm

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, February 16, 2017 - 11:15am

### Poisson equation on complete manifolds: applications to steady Ricci solitons

Geometric Analysis Learning Seminar
Thursday, February 16, 2017 - 10:00am

### Reading Seminar for Automorphic Forms

Thursday, February 16, 2017 - 8:00am

### PDE Seminar

PDE Seminar
Wednesday, February 15, 2017 - 3:35pm

### Algebraic Geometry Seminar

Algebraic Geometry
Wednesday, February 15, 2017 - 2:30pm

### Student Algebraic Topology Seminar

Special Events and Seminars
Wednesday, February 15, 2017 - 2:30pm

### Lie Theory Seminar

Lie Theory Seminar
Tuesday, February 14, 2017 - 3:35pm

### Realtime fluid simulation in the Google Chrome Web Browser

Analysis and PDE Working Seminar
Tuesday, February 14, 2017 - 2:30pm
##### Abstract:

The rise of web browsers (e.g. Chrome, Safari, Firefox) that support GPU-accelerated graphics (WebGL) has opened the floodgates (no pun intended) for realtime fluid solvers on the web. Useful for visual effects and education, what was previously only possible as a downloadable executable can now be written as a simple web page. Based off a highly cited article in Nvidia's famous "GPU Gems" collection of papers, I will discuss the general mathematical and numerical framework for realtime fluid simulation in the web browser. The talk will be mostly computational, but the numerical techniques employed give a unique perspective on the structure of the Navier-Stokes equation and a cool demo of a new frontier for accessible realtime visualization.

### Colloquium

Colloquium
Tuesday, February 14, 2017 - 2:30pm

### Colloquium

Colloquium
Tuesday, February 14, 2017 - 2:30pm

### Diferential Geometry and Symplectic Topology Seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, February 14, 2017 - 1:25pm

### Climate Change Seminar

Climate Seminar
Tuesday, February 14, 2017 - 11:15am

### Invariant Dirac operators on G/K, III

Automorphic Forms and Number Theory
Monday, February 13, 2017 - 3:35pm

### Cockburn's Seminar

Cockburn's Seminar
Monday, February 13, 2017 - 3:30pm

### MFM Student Seminar - A Student’s Crash Course on Quantitative Trading: Part 2

MCFAM Seminar
Keenan Gao, 2nd year MFM Student - University of Minnesota
Friday, February 10, 2017 - 5:30pm
##### Abstract:

This talk is the second of a two-part lecture series on the field of quantitative trading that addresses the gap: what should students know about the field in order to be able to discuss their interest with industry professionals? We will discuss the typical recruiting schedule, how to network your way into an interview opportunity, and how interviews are typically structured between different kinds of firms.

### Reading Seminar on Harmonic Analysis

Special Events and Seminars
Friday, February 10, 2017 - 3:35pm

### Ehrhart Theory for spanning lattice polytopes

Combinatorics Seminar
Lukas Katthän, Universität Frankfurt
Friday, February 10, 2017 - 3:35pm
##### Abstract:

Ehrhart Theory is the study of lattice points in polytopes. The central object of study is the Ehrhart series of a lattice polytope P, which is the generating function for the number of lattice points in the various dilations of P. It is a rational function, and the coefficients of its numerator polynomial are known as the h^*-vector of P. Our main result is that if the lattice points in P affinely span the ambient lattice, then the h^*-vector has no inner zeros. This generalizes a recent theorem by Blekherman, Smith, and Velasco, and implies a polyhedral consequence of the Eisenbud-Goto conjecture.

This is joint work with Benjamin Nill and Johannes Hofscheier.

### Applied and Computational Math Colloquium

Applied and Computational Math Colloquium
Friday, February 10, 2017 - 2:30pm

### Probability Seminar

Probability Seminar
Friday, February 10, 2017 - 2:30pm

### Startups and Machine Learning in the Wild

IMA Industrial Problems Seminar
Josh Cutler, Deep Machine
Friday, February 10, 2017 - 1:25pm
##### Abstract:

Many of the problems that you will face when applying AI in the business world are not algorithmic. This talk will draw from a variety applied machine learning scenarios that we have encountered at Deep Machine and talk about the types of problems to expect, the reasons that businesses care and some of the trade offs that we face as a small company in a big data world. It will address the breadth of work being done and discuss some of the tradeoffs between startup and big company data science.

Josh Cutler is currently the CEO and Founder of Deep Machine. He holds a BS degree in computer science and math from UW-Madison and later pursued a PhD at Duke University, where he built predictive models analyzing international conflict. He began his career commercializing research at Microsoft Live Labs. He has subsequently served in leadership roles at multiple data-focused startups, and founded and led a company to acquisition.

### Math Physics Seminar

Math Physics Seminar
Friday, February 10, 2017 - 1:25pm

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, February 9, 2017 - 4:30pm

### Colloquium

Colloquium
Thursday, February 9, 2017 - 2:30pm

### Some Recent Progress of the Uniformization Conjecture

Differential Geometry and Symplectic Topology Seminar
Gang Liu, Northwestern University
Thursday, February 9, 2017 - 1:25pm
##### Abstract:

Yau's uniformization conjecture states that a complete nonimpact Kahler manifold with positive bisectional curvature is biholomorphic to the complex Euclidean space. We survey some recent progress of this conjecture by using the Gromov-Hausdorff convergence theory. Also, we discuss some applications to noncompact Ricci flat Kahler manifolds.

### Student Number Theory Seminar

Student Number Theory Seminar
Thursday, February 9, 2017 - 12:20pm

### Welcome Week

Math Club Seminar
Thursday, February 9, 2017 - 12:20pm

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, February 9, 2017 - 11:15am

### Tutorial: 2D materials polaritons

IMA Annual Program
Tony Low, University of Minnesota, Twin Cities
Thursday, February 9, 2017 - 11:00am
##### Abstract:

In recent years, enhanced light-matter interactions through a plethora of dipole-type polaritonic excitations have been observed in two-dimensional (2D) layered materials. In graphene, electrically tunable and highly confined plasmon-polaritons were predicted and observed, opening up opportunities for optoelectronics, bio-sensing and other mid-infrared applications. In hexagonal boron nitride, low-loss infrared-active phonon-polaritons exhibit hyperbolic behavior for some frequencies, allowing for ray-like propagation exhibiting high quality factors and hyperlensing effects. In transition metal dichalcogenides, reduced screening in the 2D limit leads to optically prominent excitons with large binding energy, with these polaritonic modes having been recently observed with scanning near field optical microscopy. Here, we review recent progress in state-of- the-art experiments, survey the vast library of polaritonic modes in 2D materials, their optical spectral properties, figures-of- merit and application space. Taken together, the emerging field of 2D material polaritonics and their hybrids provide enticing avenues for manipulating light-matter interactions across the visible, infrared to terahertz spectral ranges, with new optical control beyond what can be achieved using traditional bulk materials. These tutorials will provide an introduction and overview of research in this field.

[1] Low T, Chaves A, Caldwell JD, Kumar A, Fang NX, Avouris P, Heinz TF, Guinea F, Martin-Moreno L, Koppens F. Polaritons in layered two-dimensional materials. Nature Materials. 2016 Nov 28.

### Poisson Equation on Complete Manifolds

Geometric Analysis Learning Seminar
Thursday, February 9, 2017 - 10:00am

### Reading Seminar for Automorphic Forms

Thursday, February 9, 2017 - 8:00am

### PDE Seminar

PDE Seminar
Wednesday, February 8, 2017 - 3:35pm

### Algebraic Geometry Seminar

Algebraic Geometry
Wednesday, February 8, 2017 - 2:30pm

### Student Algebraic Topology Seminar

Special Events and Seminars
Wednesday, February 8, 2017 - 2:30pm

### Tutorial: 2D materials polaritons

IMA Annual Program
Tony Low, University of Minnesota, Twin Cities
Wednesday, February 8, 2017 - 11:00am
##### Abstract:

In recent years, enhanced light-matter interactions through a plethora of dipole-type polaritonic excitations have been observed in two-dimensional (2D) layered materials. In graphene, electrically tunable and highly confined plasmon-polaritons were predicted and observed, opening up opportunities for optoelectronics, bio-sensing and other mid-infrared applications. In hexagonal boron nitride, low-loss infrared-active phonon-polaritons exhibit hyperbolic behavior for some frequencies, allowing for ray-like propagation exhibiting high quality factors and hyperlensing effects. In transition metal dichalcogenides, reduced screening in the 2D limit leads to optically prominent excitons with large binding energy, with these polaritonic modes having been recently observed with scanning near field optical microscopy. Here, we review recent progress in state-of- the-art experiments, survey the vast library of polaritonic modes in 2D materials, their optical spectral properties, figures-of- merit and application space. Taken together, the emerging field of 2D material polaritonics and their hybrids provide enticing avenues for manipulating light-matter interactions across the visible, infrared to terahertz spectral ranges, with new optical control beyond what can be achieved using traditional bulk materials. These tutorials will provide an introduction and overview of research in this field.

[1] Low T, Chaves A, Caldwell JD, Kumar A, Fang NX, Avouris P, Heinz TF, Guinea F, Martin-Moreno L, Koppens F. Polaritons in layered two-dimensional materials. Nature Materials. 2016 Nov 28.

### Lie Theory Seminar

Lie Theory Seminar
Prof. Tsao-Hsien Chen, University of Chicago
Tuesday, February 7, 2017 - 3:35pm

### Partial regularity of harmonic maps into spheres

Analysis and PDE Working Seminar
Tuesday, February 7, 2017 - 2:30pm
##### Abstract:

We will introduce the notion of harmonic maps and discuss the results of Evans on partial regularity of harmonic maps into spheres.

### Colloquium

Colloquium
Tuesday, February 7, 2017 - 2:30pm

### Colloquium

Colloquium
Tuesday, February 7, 2017 - 2:30pm

### Dictionary Design for Graph Signal Processing

IMA Data Science Lab Seminar
David Shuman, Macalester College
Tuesday, February 7, 2017 - 1:25pm
##### Abstract:

By transforming data into a new domain, techniques from statistics and signal processing such as principle components analysis and Fourier, wavelet, time-frequency, and curvelet transforms can sparsely represent and reveal relevant structural properties of time series, audio signals, images, and other data that live on regular Euclidean spaces. Such transform methods prove useful in compression, denoising, inpainting, pattern recognition, classification, and other signal processing and machine learning tasks. Unfortunately, naively applying these “classical” techniques to data on graphs would ignore key dependencies arising from irregularities in the graph data domain, and result in less informative and less sparse representations of the data. A key challenge in graph signal processing is therefore to incorporate the graph structure of the underlying data domain into dictionary designs, while still leveraging intuition from classical computational harmonic analysis techniques. In this talk, I will motivate the dictionary design problem for graph signals, examine some recently proposed dictionaries for graph signals, and discuss open issues and challenges.

David Shuman received the B.A. degree in economics and the M.S. degree in engineering-economic systems and operations research from Stanford University, Stanford, CA, USA, in 2001 and the M.S. degree in electrical engineering: systems, the M.S. degree in applied mathematics, and the Ph.D. degree in electrical engineering: systems from the University of Michigan, Ann Arbor, USA, in 2006, 2009, and 2010, respectively. He joined the Department of Mathematics, Statistics, and Computer Science, Macalester College, St. Paul, MN, USA, as an Assistant Professor in January 2014. From 2010 to 2013, he was a Postdoctoral Researcher at the Institute of Electrical Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland. His research interests include signal processing on graphs, computational harmonic analysis, and stochastic scheduling and resource allocation problems.

### Diferential Geometry and Symplectic Topology Seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, February 7, 2017 - 1:25pm

### Climate Change Seminar - NO MEETING THIS WEEK

Climate Seminar
Tuesday, February 7, 2017 - 11:15am

### Tutorial: 2D materials polaritons

IMA Annual Program
Tony Low, University of Minnesota, Twin Cities
Tuesday, February 7, 2017 - 11:00am
##### Abstract:

In recent years, enhanced light-matter interactions through a plethora of dipole-type polaritonic excitations have been observed in two-dimensional (2D) layered materials. In graphene, electrically tunable and highly confined plasmon-polaritons were predicted and observed, opening up opportunities for optoelectronics, bio-sensing and other mid-infrared applications. In hexagonal boron nitride, low-loss infrared-active phonon-polaritons exhibit hyperbolic behavior for some frequencies, allowing for ray-like propagation exhibiting high quality factors and hyperlensing effects. In transition metal dichalcogenides, reduced screening in the 2D limit leads to optically prominent excitons with large binding energy, with these polaritonic modes having been recently observed with scanning near field optical microscopy. Here, we review recent progress in state-of- the-art experiments, survey the vast library of polaritonic modes in 2D materials, their optical spectral properties, figures-of- merit and application space. Taken together, the emerging field of 2D material polaritonics and their hybrids provide enticing avenues for manipulating light-matter interactions across the visible, infrared to terahertz spectral ranges, with new optical control beyond what can be achieved using traditional bulk materials. These tutorials will provide an introduction and overview of research in this field.

[1] Low T, Chaves A, Caldwell JD, Kumar A, Fang NX, Avouris P, Heinz TF, Guinea F, Martin-Moreno L, Koppens F. Polaritons in layered two-dimensional materials. Nature Materials. 2016 Nov 28.

### Invariant Dirac operators II

Automorphic Forms and Number Theory
Monday, February 6, 2017 - 3:35pm

### Cockburn's Seminar

Cockburn's Seminar
Monday, February 6, 2017 - 3:30pm

### MFM Student Seminar - A Student’s Crash Course on Quantitative Trading: Part 1

MCFAM Seminar
Keenan Gao, 2nd Year MFM Student - University of Minnesota
Friday, February 3, 2017 - 5:30pm
##### Abstract:

This talk is the first of a two-part lecture series on the field of quantitative trading that addresses the gap: What should students know about the field in order to be able to discuss their interest with industry professionals? We will discuss the infrastructure of electronic exchanges, the distinction between buy-side and sell-side traders, the different types of trading firms, and the trading strategies that characterize these firms.

### Dimer models on cylinders over Dynkin diagrams

Combinatorics Seminar
Maitreyee Kulkarni, Louisiana State University
Friday, February 3, 2017 - 3:35pm
##### Abstract:

Let G be a Lie group of type ADE and P be a parabolic subgroup. It is known that there exists a cluster structure on the coordinate ring of the partial flag variety G/P (see the work of Geiss, Leclerc, and Schroer). Since then there has been a great deal of activity towards categorifying these cluster algebras. Jensen, King, and Su gave a direct categorification of the cluster structure on the homogeneous coordinate ring for Grassmannians (that is, when G is of type A and P is a maximal parabolic subgroup). In this setting, Baur, King, and Marsh gave an interpretation of this categorification in terms of dimer models. In this talk, I will give an analog of dimer models for groups in other types by introducing a technique called “constructing cylinders over Dynkin diagrams”, which can (conjecturally) be used to generalize the result of Baur, King, and Marsh.

### The Limit Shape of Convex Peeling

Probability Seminar
Jeff Calder, University of Minnesota
Friday, February 3, 2017 - 2:30pm
##### Abstract:

Convex peeling is an algorithm for arranging a set of points in Euclidean space into layers by repeatedly removing the vertices of the convex hull. We show that the convex peeling of random points has a large sample size continuum limit that corresponds to solving a degenerate elliptic PDE in the viscosity sense. This is joint work with Charles K. Smart (University of Chicago).

### Applied and Computational Math Colloquium

Applied and Computational Math Colloquium
Friday, February 3, 2017 - 2:30pm

### Math Physics Seminar

Math Physics Seminar
Friday, February 3, 2017 - 1:25pm

### A Sheaf Theoretic Modeling and Composition Framework for Complex Systems of Systems: Application to the Traffic Collision Avoidance

IMA Industrial Problems Seminar
Alberto Speranzon, Honeywell
Friday, February 3, 2017 - 1:25pm
##### Abstract:

The growing need and requirement of today's systems is to provide a multitude of services improving the performance of the processes they monitor and control. To achieve a scalable design paradigm most of these systems are developed by first designing, analyzing and testing subsystems and then by interconnecting them. In order to achieve scalability without completely sacrificing analytical guarantees one needs to mathematically formalize the composition operation. One of the key characteristics such a framework needs to have is the ability to easily compose different models of computation. These are conveniently used to design and analyze each subsystem, but such model may become extremely inconvenient at the time of the composition. This means that the designer needs to first choose a common abstraction model and then translate each submodel in order to compose. Contract-based design methodologies tend to be more flexible in this context, given that no explicit model of each subsystem is required and only certain 'assume-guarantee' contracts are defined. However, again, the mathematical formalization of each subcontract might be easily expressed using different formalisms, making the characterization of the contract of the composition difficult to describe.

In this talk we introduce a new framework for modeling and composing system of systems. The framework enables us to translate various mathematical submodels into a common abstraction based on interval sheaves. Leveraging the compositionality properties of sheaves we are able to define abstract machines that can be composed in an arbitrary way with strong mathematical guarantees. We introduce this framework and then show its applicability to an aerospace scenario. While the example is fairly simple, the purpose is to highlight the capability of the sheaf-based abstraction to enable composition of subsystems that are inherently described by different models of computation.

Joint work with Dr. David Spivak (MIT) and Srivatsan Varadarajan (Honeywell)

Alberto Speranzon received the ‘‘Laurea’’ degree in computer engineering from University of Padova, Italy in 2000, and a Ph.D. in automatic control from the School of Electrical Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden in 2006. In September 2015 he joined Honeywell Labs in Minneapolis, MN, USA where he is a research scientist. At Honeywell, Alberto is working on autonomous systems, leading such research area as program mana

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, February 2, 2017 - 4:30pm

### Colloquium

Colloquium
Thursday, February 2, 2017 - 2:30pm

### Diferential Geometry and Symplectic Topology Seminar

Differential Geometry and Symplectic Topology Seminar
Thursday, February 2, 2017 - 1:25pm

### Welcome Week

Math Club Seminar
Thursday, February 2, 2017 - 12:20pm

### Student Number Theory Seminar

Student Number Theory Seminar
Thursday, February 2, 2017 - 12:20pm

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, February 2, 2017 - 11:15am

### A Gap Theorem for Gradient Ricci Shrinkers of Dimension Four

Geometric Analysis Learning Seminar
Thursday, February 2, 2017 - 10:00am
##### Abstract:

We will talk about the recent result of Y. Li and B. Wang (https://arxiv.org/abs/1701.01989), which shows that nontrivial flat cones cannot be approximated by smooth Ricci shrinkers with bounded scalar curvature in dimension 4.

### Planar propagating terraces and the dynamics of front-like solutions of parabolic equations

PDE Seminar
Wednesday, February 1, 2017 - 3:35pm
##### Abstract:

We consider bounded front-like solutions of parabolic equations $u_t=\Delta u+f(u)$ on $\mathbb R^N$. Front-like solutions are solutions with initial data $u_0(x_1,x_2,\dots,x_N)$ whose limits as $x_1\to\pm\infty$ exist, uniformly in $(x_2,\dots,x_N)$, and are equal to distinct zeros of $f$. If $N=1$, we show a general result on the approach of front-like solutions to propagating terraces, or, stacked families of traveling fronts. For $N\ge 2$, we use the propagating terraces of the one-dimensional problem, or, planar propagating terraces, to show the asymptotic one-dimensional symmetry of front-like solutions and related results.

### Algebraic Geometry Seminar

Algebraic Geometry
Wednesday, February 1, 2017 - 2:30pm

### Student Algebraic Topology Seminar

Special Events and Seminars
Wednesday, February 1, 2017 - 2:30pm

### Colloquium

Colloquium
Tuesday, January 31, 2017 - 2:30pm

### Analysis and PDE Working Seminar

Analysis and PDE Working Seminar
Tuesday, January 31, 2017 - 2:30pm

### Colloquium

Colloquium
Tuesday, January 31, 2017 - 2:30pm

### Diferential Geometry and Symplectic Topology Seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, January 31, 2017 - 1:25pm

### Climate Change Seminar

Climate Seminar
Tuesday, January 31, 2017 - 11:15am

### Invariant Dirac operators on G/K

Automorphic Forms and Number Theory
Monday, January 30, 2017 - 3:35pm

### Cockburn's Seminar

Cockburn's Seminar
Monday, January 30, 2017 - 3:30pm

### Automorphic Forms and Number Theory

Automorphic Forms and Number Theory
Monday, January 30, 2017 - 3:30pm

tba

### MCFAM Seminar - No Seminar

MCFAM Seminar
Friday, January 27, 2017 - 5:30pm

### Old Problems on Multiplicities and New Families of Tableaux

Combinatorics Seminar
Se-Jin Oh, Ewha Womans University
Friday, January 27, 2017 - 3:35pm
##### Abstract:

Computing weight multiplicities of dominant weight of highest weight modules over finite simple Lie algebra is quite old problem. Weyl's character formula and Freudenthal's formula give a way to compute such weight multiplicities, which looks not so practical. The crystal basis theory and it's related combinatorics, initiated by Kashiwara in the beginning of 1990, provide alternative way to compute such weight multiplicities. For example, by enumerating Kashiwara-Nakashima tableaux with a fixed weight, one can compute weight multiplicities. But the description of Kashiwara-Nakashima tableaux is somewhat complicated. Thus it looks difficult to compute multiplicities by using Kashiwara-Nakashima tableaux in general.

In the joint work of Kyu-Hwan Lee and Jangsoo Kim, we suggest new families of tableaux, called (spin-)rigid tableaux, which are subsets of standard (skew) Young tableaux and are equinumerous to weight multiplicities of certain infinite families of highest modules over finite finite simple Lie algebra types B and D. Moreover, we can give explicit and closed formulas for certain subfamilies of them. Interestingly, they form Pascal, Catalan, Motzkin, Riordan(newly defined by ourselves) and Bessel triangular arrays.

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, January 26, 2017 - 4:30pm

### Geometry on the space of Kahler metrics and applications to canonical metrics

Colloquium
Tamas Darvas, University of Maryland
Thursday, January 26, 2017 - 3:30pm
##### Abstract:

A basic problem in Kahler geometry, going back to Calabi in the 50's, is to find Kahler metrics with the best curvature properties, e.g., Einstein metrics. Such special metrics are minimizers of well known functionals on the space of all Kahler metrics H. However these functionals become convex only if an adequate geometry is chosen on H. One such choice of Riemannian geometry was proposed by Mabuchi in the 80's, and was used to address a number of uniqueness questions in the theory. In this talk I will present more general Finsler geometries on H, that still enjoy many of the properties that Mabuchi's geometry has, and I will give applications related to existence of special Kahler metrics, including the recent resolution of Tian's related properness conjectures.

### Symplectic Deformation of simple Hamiltonian-S^1 Manifolds

Differential Geometry and Symplectic Topology Seminar
Heidi Andersen, UMN
Thursday, January 26, 2017 - 1:25pm
##### Abstract:

Recently, an interesting symplectic deformation on simple Hamiltonian-S^1 manifolds of dimension 6 was constructed and described. It had the auspicious property of producing a deformation equivalence between a Kaehler form and a symplectic form that was not Hard Lefschetz, thereby answering a question from Khesin and McDuff in the 1990s. I will present work on extending this result to dimensions 8 and higher.

### Welcome Week

Math Club Seminar
Thursday, January 26, 2017 - 12:20pm

### Student Number Theory Seminar

Student Number Theory Seminar
Thursday, January 26, 2017 - 12:20pm

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, January 26, 2017 - 11:15am

### Structure at Infinity for Shrinking Ricci Solitons

Geometric Analysis Learning Seminar
Thursday, January 26, 2017 - 10:00am

### PDE Seminar

PDE Seminar
Wednesday, January 25, 2017 - 3:35pm

### Algebraic Geometry Seminar

Algebraic Geometry
Wednesday, January 25, 2017 - 2:30pm

### Student Algebraic Topology Seminar

Special Events and Seminars
Wednesday, January 25, 2017 - 2:30pm

### Recent Progress in Representation Stability

Colloquium
Andrew Snowden, University of Michigan, Ann Arbor
Tuesday, January 24, 2017 - 3:30pm
##### Abstract:

Representation stability is a relatively new field that studies somewhat exotic algebraic structures and exploits their properties to prove results (often asymptotic in nature) about objects of interest. I will describe some of the algebraic structures that appear (and state some important results about them), give a sampling of some notable applications (in group theory, topology, and algebraic geometry), and mention some open problems in the area.

### What is special about mining spatial and spatio-temporal datasets?

IMA Data Science Lab Seminar
Shashi Shekhar, University of Minnesota, Twin Cities
Tuesday, January 24, 2017 - 1:25pm
##### Abstract:

The importance of spatial and spatio-temporal data mining is growing with the increasing incidence and importance of large datasets such as trajectories, maps, remote-sensing images, census and geo-social media. Applications include Public Health (e.g. monitoring spread of disease, spatial disparity, food deserts), Public Safety (e.g. crime hot spots), Public Security (e.g. common operational picture), Environment and Climate (change detection, land-cover classification), M(obile)-commerce (e.g. location-based services), etc.
Classical data mining techniques often perform poorly when applied to spatial and spatio-temporal data sets because of the many reasons. First, these dataset are embedded in continuous space with implicit relationships, whereas classical datasets (e.g. transactions) are often discrete. Second, the cost of spurious patterns (e.g., false positives, chance patterns) is often high in spatial application domains. In addition, one of the common assumptions in classical statistical analysis is that data samples are independently generated. When it comes to the analysis of spatial and spatio-temporal data, however, the assumption about the independence of samples is generally false because such data tends to be highly self correlated. For example, people with similar characteristics, occupation and background tend to cluster together in the same neighborhoods. In spatial statistics this tendency is called autocorrelation. Ignoring autocorrelation when analyzing data with spatial and spatio-temporal characteristics may produce hypotheses or models that are inaccurate or inconsistent with the data set.

Thus new methods are needed to analyze spatial and spatio-temporal data to discover interesting, useful and non-trivial patterns. This talk surveys some of the new methods including those for discovering hotspots (e.g., circular, linear, rings), interactions (e.g. co-locations , co-occurrences, tele-connections), detecting spatial outliers and location prediction along with emerging ideas on spatio-temporal pattern mining.

Shashi Shekhar is a Mcknight Distinguished University Professor at the University of Minnesota (Computer Science faculty). For contributions to geographic information systems (GIS), spatial databases, and spatial data mining, he was elected an IEEE Fellow as well as an AAAS Fellow and received the IEEE-CS Technical Achievement Award, and the UCGIS Education Award. He was also named a key difference-maker for the field of

### Climate Change Seminar

Climate Seminar
Tuesday, January 24, 2017 - 11:15am

### Automorphic Forms & Number Theory [will not meet]

Automorphic Forms and Number Theory
Monday, January 23, 2017 - 3:35pm

Room tba

### Integral Structures on DeRham Cohomology

Automorphic Forms and Number Theory
Prof. Andrew Snowden, University of Michigan
Monday, January 23, 2017 - 3:35pm
##### Abstract:

Given a smooth projective variety X over a number field K, we construct two canonical O_K-lattices in the algebraic de Rham cohomology of X. The first is constructed using the p-adic comparison theorems (for all p). The second is constructed geometrically, but the proof that it is a lattice uses the p-adic comparison theorems. Both constructions have more elementary analogs in complex geometry that I will discuss first. This is joint work with Bhargav Bhatt.

### Cockburn's Seminar

Cockburn's Seminar
Monday, January 23, 2017 - 3:30pm

### MCFAM Seminar - No Seminar

MCFAM Seminar
Friday, January 20, 2017 - 5:30pm

### The effect of clamped intervals on the representations of posets

Combinatorics Seminar
Friday, January 20, 2017 - 3:35pm
##### Abstract:

In work with Kos Diveris and Marju Purin we show that subintervals of a poset satisfying a condition that we call 'clamped' determine a part of the representation theory of the whole poset, to the extent that we can determine the Auslander-Reiten quivers of the bounded derived category and of the module category in favorable circumstances. The approach allows us to construct lattices with quivers of arbitrary tree class (up to barycentric subdivision), as well as lattices of finite representation type, derived equivalent to quivers of wild representation type

### Exploring Citation Networks

IMA Industrial Problems Seminar
Isabelle Moulinier, Xin Shuai, Thomson Reuters, Thomson Reuters
Friday, January 20, 2017 - 1:25pm
##### Abstract:

Citation graphs are at the core of expert knowledge propagation and verification, regardless of domain, whether legal or scientific. We discuss two projects that explore citation graphs. Specifically, we define the problems, propose our methodology, as well as demonstrate the challenges and results. The first project looks at legal precedent, and the second focuses on the impact of scientific retraction.

### Turbulent Weak Solutions of the Euler Equations

Colloquium
Thursday, January 19, 2017 - 3:30pm
##### Abstract:

Motivated by Kolmogorov's theory of hydrodynamic turbulence, we consider dissipative weak solutions to the 3D incompressible Euler equations. We show that there exist infinitely many weak solutions of the 3D Euler equations, which are continuous in time, lie in a Sobolev space $H^s$ with respect to space, and they do not conserve the kinetic energy. Here the smoothness parameter $s$ is at the Onsager critical value $1/3$, consistent with Kolmogorov's $-4/5$ law for the third-order structure functions. We shall also discuss bounds for the second order structure functions, which deviate from the classical Kolmogorov 1941 theory. This talk is based on joint work with T. Buckmaster and N. Masmoudi.

### Geodesics on Surfaces

Colloquium
Jenya Sapir, University of Illinois, Urbana
Thursday, January 19, 2017 - 2:00pm
##### Abstract:

Let S be a hyperbolic surface. We will give a history of counting results for geodesics on S. In particular, we will give estimates that fill the gap between the classical results of Margulis and the more recent results of Mirzakhani. We will then give some applications of these results to the geometry of curves. In the process we highlight how combinatorial properties of curves, such as self-intersection number, influence their geometry.

### Math Club Welcome Week

Math Club Seminar
Thursday, January 19, 2017 - 12:20pm

### Commutative Algebra Seminar - No Seminar

Commutative Algebra Seminar
Thursday, January 19, 2017 - 11:15am

### Superlensing Using Hyperbolic Metamaterials

IMA Annual Program
Eric Bonnetier, Université Grenoble-Alpes
Thursday, January 19, 2017 - 11:00am
##### Abstract:

We discuss super-lensing in composite media, i.e., the possibility of imaging an arbitrary object without imposing any conditions on size of the object and the wave length. We are particularly interested in lenses made of hyperbolic metamaterials and propose two devices that exhibit superlensing properties. This is joint work with Hoai-Min Nguyen (EPFL).

### Geometric Analysis Learning Seminar

Geometric Analysis Learning Seminar
Thursday, January 19, 2017 - 10:00am

### PDE Seminar

PDE Seminar
Wednesday, January 18, 2017 - 3:35pm

### Climate Change Seminar

Climate Seminar
Tuesday, January 17, 2017 - 11:15am

### Automorphic Forms and Number Theory

Automorphic Forms and Number Theory
Monday, January 16, 2017 - 3:35pm

### MCFAM Seminar

MCFAM Seminar
Friday, January 13, 2017 - 5:30pm

### Commutative Algebra Seminar - No Seminar

Commutative Algebra Seminar
Thursday, January 12, 2017 - 11:15am

### Climate Change Seminar

Climate Seminar
Tuesday, January 10, 2017 - 11:15am

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, January 5, 2017 - 11:15am

### Climate Change Seminar

Climate Seminar
Tuesday, January 3, 2017 - 11:15am

### MCFAM Seminar

MCFAM Seminar
Friday, December 30, 2016 - 5:30pm

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, December 29, 2016 - 11:15am

### Climate Change Seminar

Climate Seminar
Tuesday, December 27, 2016 - 11:15am

### MCFAM Seminar - No Seminar

MCFAM Seminar
Friday, December 23, 2016 - 5:30pm

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, December 22, 2016 - 11:15am

### Climate Change Seminar

Climate Seminar
Tuesday, December 20, 2016 - 11:15am

### Plane wave approximation of homogeneous Helmholtz solutions

Cockburn's Seminar
Monday, December 19, 2016 - 2:00pm
##### Abstract:

We establish error estimates for the approximation of solutions of the Helmholtz equation by linear combinations of plane waves. The estimates combine approximation results of Helmholtz solutions by generalized harmonic polynomials, via Vekua theory, and approximation of generalized harmonic polynomials by plane waves.

### Reading Seminar for Automorphic Forms

Monday, December 19, 2016 - 9:00am

### MCFAM Seminar

MCFAM Seminar
Friday, December 16, 2016 - 5:30pm

### Lie Theory Seminar

Lie Theory Seminar
Friday, December 16, 2016 - 3:30pm

### Applied and Computational Math Colloquium

Applied and Computational Math Colloquium
Friday, December 16, 2016 - 2:30pm

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, December 15, 2016 - 4:40pm

### Colloquium

Colloquium
Thursday, December 15, 2016 - 3:30pm

### Algebraic Geometry Reading Group Seminar

Thursday, December 15, 2016 - 2:30pm

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Thursday, December 15, 2016 - 1:25pm

### Math Physics Seminar

Math Physics Seminar
Thursday, December 15, 2016 - 12:20pm

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, December 15, 2016 - 11:15am

### Geometric Analysis Learning Seminar

Geometric Analysis Learning Seminar
Thursday, December 15, 2016 - 11:10am

### Large time behavior of Trudinger's equation

PDE Seminar
Ryan Hynd, University of Pennsylvania
Wednesday, December 14, 2016 - 3:30pm
##### Abstract:

We will study the large time behavior of a homogeneous doubly nonlinear flow. This equation is among a class of
nonlinear parabolic PDE for which Trudinger established a Harnack inequality by generalizing previous work of Moser.
We will show that the large time behavior is tied to equality conditions of an optimal Poincaré inequality and its "dual." Conversely,
we will explain how to write down a flow that will help approximate the optimal constant for any Poincaré type inequality and its extremal
functions. Time permitting, we will discuss applications to nonlocal equations and to the operator norm of the Sobolev trace mapping.

### Algebraic Geometry Seminar

Algebraic Geometry
Wednesday, December 14, 2016 - 2:30pm

### Algebraic Geometry Seminar

Algebraic Geometry
Wednesday, December 14, 2016 - 2:30pm

### Self-Adjoint Operators on a Modular Curve: why a number theorist is allowed to talk in a PDE Seminar

Student PDE Seminar
Wednesday, December 14, 2016 - 11:10am
##### Abstract:

It was speculated by Hilbert and Polya that one might solve the Riemann Hypothesis by finding self-adjoint operator whose spectral parameters contained zeros of zeta. However, little progress has been made in this direction due to a lack candidate operators. In 1977 a computational mistake inspired some recent traction by Bombieri and Garrett.

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, December 13, 2016 - 1:25pm

### Climate Change Seminar

Climate Seminar
Tuesday, December 13, 2016 - 11:15am

### [will not meet]

Automorphic Forms and Number Theory
Monday, December 12, 2016 - 3:35pm

### Approximating Functions with Singularities

Cockburn's Seminar
Monday, December 12, 2016 - 3:35pm
##### Abstract:

Title: Approximating Functions with Singularities

### Topology Seminar

Topology Seminar
Monday, December 12, 2016 - 2:30pm

### Student Number Theory Seminar

Student Number Theory Seminar
Monday, December 12, 2016 - 12:20pm

### Reading Seminar for Automorphic Forms

Monday, December 12, 2016 - 9:00am

### A reduced-form model for level-1 limit order books

MCFAM Seminar
Tzu-Wei Yang, MCFAM
Friday, December 9, 2016 - 5:30pm
##### Abstract:

One popular approach to model the limit order books dynamics of the
best bid and ask at level-1 is to use the reduced-form diffusion
approximations. It is well known that the biggest contributing factor
to the price movement is the imbalance of the best bid and ask. We
investigate the data of the level-1 limit order books of a basket of
stocks and study the numerical evidence of drift, correlation,
volatility and their dependence on the imbalance. Based on the
numerical discoveries, we develop a nonparametric discrete model for
the dynamics of the best bid and ask, which can be approximated by a
reduced-form model with analytical tractability that can fit the
empirical data of correlation, volatilities and probability of price
movement simultaneously.

This is a joint work with Prof. Lingjiong Zhu.

Bio: Dr. Tzu-Wei Yang was a post-doctoral fellow at Stanford University's Department of Mathematics prior to joining MCFAM. He got his PhD from the Institute for Computational and Mathematical Engineering at Stanford University where his advisor was Dr. George C. Papanicolaou, the Robert Grimmett Professor of Mathematics at Stanford. Dr. Yang's research interests cover stochastic differential equations, financial mathematics and uncertainty quantification. Dr. Yang also has a B.S in Applied Mathematics from National Chiao Tung University, and an MS in Electrical Engineering from National Taiwan University in Taiwan.

More details on his current research can be found at:http://math.umn.edu/~yangx953/

### A rational lift of the combinatorial R-matrix

Combinatorics Seminar
Gabriel Frieden, University of Michigan
Friday, December 9, 2016 - 3:35pm
##### Abstract:

The combinatorial R-matrix is the unique affine $\mathfrak{sl}_n$ crystal isomorphism between $B_1 \otimes B_2$ and $B_2 \otimes B_1$, where $B_1$ and $B_2$ are finite-dimensional affine crystals corresponding to rectangular partitions. This map can be described combinatorially in terms of rectification of skew tableaux.

In this talk, I will present a construction of a geometric R-matrix,'' a rational map which has properties analogous to those of the combinatorial R-matrix, and which tropicalizes to give a piecewise-linear formula for the combinatorial R-matrix. The construction makes use of Noumi and Yamada's notion of tropical row insertion,'' as well as the Grassmannian and the loop group. When both partitions are a single row, we recover results of Yamada and Lam-Pylyavskyy.

### Lie Theory Seminar

Lie Theory Seminar
Friday, December 9, 2016 - 3:30pm

### Applied and Computational Math Colloquium

Applied and Computational Math Colloquium
Friday, December 9, 2016 - 2:30pm

### Recent Advances in Symmetrization Techniques for Nonlocal Equations

Probability Seminar
Bruno Volzone, Università degli Studi di Napoli "Parthenope"
Friday, December 9, 2016 - 2:30pm
##### Abstract:

Symmetrization techniques are nowadays widely renowned for being very efficient tools to get sharp estimates for solutions to PDE. In the first part of this talk, excerpted from the joint work with G. Di Blasio, we shall describe how symmetrization techniques allow to get a concentration comparison result for solutions of elliptic equations involving the fractional Laplacian, of the type $(-\Delta)^{\alpha/2}u=f$ posed in an open bounded set $\Omega$ of R^N and 0 < \alpha < 2, with homogeneous Dirichlet boundary conditions. The data f is assumed to belong to a suitable Lorentz space $L^{p,q}(\Omega)$. These results will be useful to easily obtain, as a natural consequence, some regularity results for the solutions in terms of the data f, generalizing the classical results for the Laplacian. The second part of the talk will focus on the main topics of some recent joint works with J. L. Vázquez in which we consider the application of symmetrization techniques to obtaining concentration comparison results for linear and nonlinear parabolic equations with fractional diffusion, of the form $u_{t}+(-\Delta)^{\alpha/2}A(u)=f$, taking into account several assumptions on the nonlinearity $A:\R_{+}\rightarrow\R_{+}$. Moreover, we will show some very recent results where Neumann boundary conditions are assumed. Finally, we will sketch some work in progress in the theory, concerning the application of these methods to nonlocal operators related to the the gaussian measure.

### Soumitri Kolavennu: Critical Node Analysis and Mitigation in Industrial Wireless Sensor Networks (Applications of Spectral Graph theory)

IMA Industrial Problems Seminar
Soumitri Kolavennu, Honeywell
Friday, December 9, 2016 - 1:25pm
##### Abstract:

Honeywell’s automation and control solutions unit consists of a number businesses where wireless sensor networks are utilized. These wireless networks provide total install cost savings for the business and its customers. In addition, during operation the systems are more robust to link and node failures. Wireless sensor networks are employed in industrial control and data acquisition systems, hotel management networks, automated meter reading networks, building scale fire and life safety systems etc.

The wireless sensor networks are deployed as mesh networks where the sensor and actuator nodes can talk to each other neighbors and reach destination nodes which are typically gateways where the data is consumed. Mesh networks are desirable because of the inherent ability of the network to reconfigure itself around a faulted node or a link and still be able to reach the gateway. However such guarantees are only possible when there are no critical nodes (nodes that split the network into disjoint clusters). This talk concentrates on ability of the network management functions to detect critical nodes quickly and provide mitigation for the critical nodes and links using spectral graph theory. Other applications of spectral graph theory for these networks are also discussed. The main motivation of the presentation is to present the typical kinds of problems in practical implementation of sensor networks in the automation and control industries.

Soumitri Kolavennu joined Honeywell in 1999, initially as a student intern. His areas of expertise include wireless, voice, and advanced control.  His early work in wireless mesh networking and wireless localization enabled ACS products like OneWireless™ and Impact Xtreme to be differentiated in the marketplace. Recently, He has been a key contributor to Honeywell’s Connected Home offerings, specifically the Voice recognition and Home Kit based thermostats. He was the primary contributor and editor for the Networking and Provisioning Layers of the ISA100.11a standard for industrial wireless sensor networks and he has helped draft standards relevant to the smart grid and energy management systems. He is a member of the Standards Subcommittee of IEEE Control Systems Society and a past member of the Smart Grid Architecture Committee (SGAC) for the NIST Smart Grid Interoperability Panel (SGIP). He is the fellows leader for Homes and Building technologies with in Honeywell. He has over 50 issued patents. His publications

### Marc Light: Lecture

IMA Industrial Problems Seminar
Marc Light, Honeywell
Friday, December 9, 2016 - 1:25pm

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, December 8, 2016 - 4:40pm

### Colloquium

Colloquium
Thursday, December 8, 2016 - 3:30pm

### BMO solvability and absolute continuity of harmonic measure

PDE Seminar
Steven Hofmann, University of Missouri
Thursday, December 8, 2016 - 2:30pm
##### Abstract:

For a uniformly elliptic divergence form operator $L$, defined in an open set
$\Omega$ with Ahlfors-David regular boundary, we show that BMO-solvability implies scale invariant quantitative absolute continuity (the weak-$A_\infty$ property) of elliptic-harmonic measure with respect to surface measure on $\partial \Omega$. We do not impose any connectivity hypothesis, qualitative or quantitative; in particular, we do not assume the Harnack Chain condition, even within individual connected components of $\Omega$.
In this generality, our results are new even for the Laplacian. Moreover, we obtain a converse, under the additional assumption that $\Omega$ satisfies an interior Corkscrew condition, in the special case that $L$ is the Laplacian. This is joint work with Phi Le.

### Algebraic Geometry Reading Group Seminar

Thursday, December 8, 2016 - 2:30pm

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Thursday, December 8, 2016 - 1:25pm

### SIAM Student Chapter Reading Group Seminar

Thursday, December 8, 2016 - 1:25pm
##### Abstract:

12/8/16 Seminar Location Change to 140 Nolte Center for Continuing Education

### Green's Functions In Curved Spacetimes And Gravitational Waves

Math Physics Seminar
Yi-Zen Chu, U of M Duluth
Thursday, December 8, 2016 - 12:20pm
##### Abstract:

Green's functions lie at the heart of constructing (perturbative) solutions to both linear and nonlinear wave equations of mathematical physics. In curved spacetimes, they are also key to understanding the causal structure of their radiative wave solutions: for, despite having a zero rest mass, photons and gravitons travel both on and within the null cone in a generic curved geometry. (This inside-the-null cone propagation of waves is called the "tail effect" and is also sometimes described as a violation of Huygens' principle.) I will explain, in particular, why Green's functions in black hole (BH) geometries play a crucial role in understanding the gravitational waves (GWs) emitted from the super-massive BHs that astronomers now believe reside at the center of most (if not all) galaxies, including our own. Within the next 2 decades, humanity may have the means -- by orbiting very large scale GW detectors around the Sun -- to directly hear such vibrations of spacetime. I am developing a research program to explore novel methods to compute curved spacetime Green's functions, and will review some of my results.

### Math Club

Math Club Seminar
Thursday, December 8, 2016 - 12:20pm

### Uniform Asymptotic Growth on Symbolic Powers of Ideals

Commutative Algebra Seminar
Thursday, December 8, 2016 - 11:15am
##### Abstract:

More recently, my dissertation (e.g., arxiv.org/1510.02993, arxiv.org/1608.02320) attempts to devise--and establish affirmative results towards--a "toric" variant of a short-lived conjecture of Brian Harbourne (2009) that says: For N \ge 2, the symbolic power I^{(N(r-1)+1)} lies in I^r for all r>0 and all graded ideals I in the coordinate ring R of a projective N-space over a field (sometimes arbitrary, sometimes not). This talk will discuss criteria for ideal containments of type I^{(E(r-1)+1)} \subseteq I^r for all r>0: at the expense of focusing rigidly on a very specific type of ideal, I can give you a duly explicit slope E. These criteria already apply to a fairly prodigious class of normal domains (e.g., several with European-honorific names).

### Geometric Analysis Learning Seminar

Geometric Analysis Learning Seminar
Thursday, December 8, 2016 - 11:10am

### SIAM Student Chapter Reading Group Seminar

Thursday, December 8, 2016 - 7:30am

### Phase separation patterns from directional quenching

PDE Seminar
Rafael Monteiro, University of Minnesota
Wednesday, December 7, 2016 - 3:30pm
##### Abstract:

We study the effect of directional quenching on patterns formed in simple bistable systems such as the Allen-Cahn and the Cahn-Hilliard equation on the plane. We model directional quenching as an externally triggered change in system parameters, changing the system from monostable to bistable across an interface. We are then interested in patterns forming in the bistable region, in particular as the trigger progresses and increases the bistable region. We find existence and non-existence results of single interfaces and striped patterns. Joint work with Arnd Scheel.

### Lifting laws, arithmetic invariant theory, and L-functions

Lie Theory Seminar
Aaron Pollack, Stanford University
Wednesday, December 7, 2016 - 3:30pm
##### Abstract:

I will discuss, by way of examples, how arithmetic invariant theory seems to play a non-trivial role in the theory of integral representations of L-functions. The examples include results of many people, such as Andrianov, Avner Segal, and myself. With these examples as motivation, I will then discuss my recent work on twisted versions of some of the orbit parametrization theorems of Bhargava. The main technical ingredient in the proof of these parametrizations is a "lifting law", which is a way of relating elements in the open orbit of one prehomogeneous vector space with elements in the minimal orbit of another prehomogeneous vector space.

### A New Discriminant Algebra Construction

Algebraic Geometry
Wednesday, December 7, 2016 - 2:30pm
##### Abstract:

For a finite separable field extension in characteristic other than 2, its discriminant field controls whether its Galois closure has Galois group contained in the alternating group. In the last decade, Rost, Deligne, and Loos have suggested generalizations of the discriminant field to a "discriminant algebra" defined for general branched covers of schemes. We present a new construction of a discriminant algebra and discuss its relation to those defined by Rost and Loos. This is joint work with Alberto Gioia.

### A New Discriminant Algebra Construction

Algebraic Geometry
Wednesday, December 7, 2016 - 2:30pm
##### Abstract:

For a finite separable field extension in characteristic other than 2, its discriminant field controls whether its Galois closure has Galois group contained in the alternating group. In the last decade, Rost, Deligne, and Loos have suggested generalizations of the discriminant field to a "discriminant algebra" defined for general branched covers of schemes. We present a new construction of a discriminant algebra and discuss its relation to those defined by Rost and Loos. This is joint work with Alberto Gioia.

### Frechet Differentiability in the Optimal Control of the Stefan Problem

Student PDE Seminar
Wednesday, December 7, 2016 - 11:10am
##### Abstract:

In this talk I will give a heuristic derivation for the Frechet gradient in the optimal control of a Stefan-type free boundary problem. I will introduce the notion of the adjoint problem, which is analogous to the method of Lagrange multipliers. I will show how the heuristic derivation can be used to prove the derivative formula rigorously. This work was completed as part of an REU at the Florida Institute of Technology led by Professor Ugur Abdulla.

### Arithmetic Invariant Theory

Colloquium
Aaron Pollack, Stanford University
Tuesday, December 6, 2016 - 1:30pm
##### Abstract:

Arithmetic invariant theory is, roughly, the study of the orbits of groups like GL_n(Z) on lattices inside the finite dimensional representations of GL_n(R). While simply stated, these orbit problems turn out to be delicate and interesting. I will give an introduction to and partial survey of this field. In particular, I will highlight "Gauss composition" on binary quadratic forms, and some of the seminal contributions of Bhargava on "Higher composition laws".

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, December 6, 2016 - 1:25pm

### Climate Change Seminar

Climate Seminar
Tuesday, December 6, 2016 - 11:15am

### Variable coefficients and numerical methods for electrmagnetic waves

Special Events and Seminars
Tuesday, December 6, 2016 - 11:15am
##### Abstract:

In the first part of the talk, we will discuss a numerical method for
wave propagation in inhomogeneous media. The Trefftz method relies on
basis functions that are solution of the homogeneous equation. In the
case of variable coefficients, basis functions are designed to solve an
approximation of the homogeneous equation. The design process yields
high order interpolation properties for solutions of the homogeneous
equation. This introduces a consistency error, requiring a specific
analysis.

In the second part of the talk, we will discuss a numerical method for
elliptic partial differential equations on manifolds. In this framework
the geometry of the manifold introduces variable coefficients. Fast,
high order, pseudo-spectral algorithms were developed for inverting the
Laplace-Beltrami operator and computing the Hodge decomposition of a
tangential vector field on closed surfaces of genus one in a three
dimensional space. Robust, well-conditioned solvers for the Maxwell
equations will rely on these algorithms.

### [will not meet]

Automorphic Forms and Number Theory
Monday, December 5, 2016 - 3:35pm

### Approximating Functions with Singularities

Cockburn's Seminar
Monday, December 5, 2016 - 3:35pm
##### Abstract:

Title: Approximating Functions with Singularities

### Student Number Theory Seminar

Student Number Theory Seminar
Monday, December 5, 2016 - 12:20pm

### Quantization of the Modular Functor and Equivariant Elliptic Cohomology

Topology Seminar
Nitu Kitchloo, Johns Hopkins University
Monday, December 5, 2016 - 12:20pm
##### Abstract:

Let M be a compact G-space for a compact Lie group G. I will describe a procedure that can be seen as the categorical quantization of the category of parametrized positive energy representations of the loop group of G. This procedure is described in terms of dominant K-theory of the loop group parametrized over M. More concretely, I will construct a holomorphic sheaf over a universal elliptic curve with values in dominant K-theory of the loop space LM, and show that each stalk of this sheaf is a cohomological functor of M (thereby giving rise to an equivariant cohomology theory). I will also give compelling evidence that this theory is equivalent to equivariant elliptic cohomology of M as constructed by Grojnowski. I will assume very little background, and give a lot of motivation, but some general ideas of what a field theory is may be helpful.

REMINDER: This talk is at 12:20!

### Alexander Cloninger: Incorporation of Geometry into Learning Algorithms and Medicine

IMA Data Science Lab Seminar
Alexander Cloninger, Yale University
Monday, December 5, 2016 - 11:15am
##### Abstract:

This talk focuses on two instances in which scientific fields outside mathematics benefit from incorporating the geometry of the data. In each instance, the applications area motivates the need for new mathematical approaches and algorithms, and leads to interesting new questions. (1) A method to determine and predict drug treatment effectiveness for patients based off their baseline information. This motivates building a function adapted diffusion operator high dimensional data X when the function F can only be evaluated on large subsets of X, and defining a localized filtration of F and estimation values of F at a finer scale than it is reliable naively. (2) The current empirical success of deep learning in imaging and medical applications, in which theory and understanding is lagging far behind. By assuming the data lies near low dimensional manifolds and building local wavelet frames, we improve on existing theory that breaks down when the ambient dimension is large (the regime in which deep learning has seen the most success).

### Reading Seminar for Automorphic Forms

Monday, December 5, 2016 - 9:00am

### Industry Competition, Profitability and Stock Returns

MCFAM Seminar
Friday, December 2, 2016 - 5:30pm
##### Abstract:

Speaker: Yao Deng

Affiliation: UMN Carlson PhD in Finance Candidate/MCFAM MFM Alumnus

Bio: Yao Deng is currently a third year finance PhD student at University of Minnesota. His research interests include empirical and theoretical asset pricing, macro finance and behavioral finance. He holds a master in financial mathematics from University of Minnesota and a bachelor in economics and mathematics from Central University of Finance and Economics in Beijing.

### The orbit method via deformations of singular symplectic varieties

Lie Theory Seminar
Ivan Loseu, Northeastern University
Friday, December 2, 2016 - 3:30pm
##### Abstract:

One of the cornerstones of the infinite dimensional Lie representation theory is Kirillov's Orbit method (1961). It says that the irreducible unitary representations of a nilpotent Lie group are in a natural bijection with the orbits of the coadjoint action of that group. There is an analog of this result for nilpotent Lie algebras, due to Dixmier (1963): instead of unitary representations one considers so called primitive ideals ( = annihilators of irreducible modules) in universal enveloping algebras.

An immediate question is how to generalize these results to semisimple Lie groups or Lie algebras. I will talk about the Lie algebra case. My recent result here is that there is a natural map from the set of (co)adjoint orbits to the set of primitive ideals which is known to be injective in almost all cases (for example, for classical Lie algebras). To produce this map I compare commutative and noncommutative deformations of singular symplectic varieties, a spectacular class of singular algebraic varieties introduced by Beauville in 2000.

### Stefan Steinerberger: Elliptic PDEs and Diffusion: Short Proofs by Counting Particles and Applications

IMA Data Science Lab Seminar
Friday, December 2, 2016 - 2:30pm
##### Abstract:

We describe a simple trick in the study of elliptic PDEs: introduce time and interpret the solution of the elliptic pde as a fixed point of the evolution of the parabolic equation. We illustrate this technique by giving extremely short proofs of some classical results, an alternative interpretation of the Filoche-Mayboroda landscape function and improvements of classical results of Makai, Hayman and E. Lieb (originally conjectured by Polya & Szego). Finally, we discuss applications in data science (related to properties of eigenfunctions of Graph Laplacians on graphs constructed from real-life data).

### Applied and Computational Math Colloquium

Applied and Computational Math Colloquium
Friday, December 2, 2016 - 2:30pm

### Exotic cluster algebras

Combinatorics Seminar
Idan Eisner, University of Haifa
Friday, December 2, 2016 - 2:30pm
##### Abstract:

Cluster algebras are commutative rings with a distinguished set of generators that are grouped into overlapping finite sets of the same cardinality. Among many other examples, cluster algebras appear in coordinate rings of various algebraic varieties. Using the notion of compatibility between Poisson brackets and cluster algebras in the coordinate rings of simple complex Lie groups, Gekhtman Shapiro and Vainshtein conjectured a correspondence between the two. Poisson Lie groups are classified by the Belavin-Drinfeld classification of solutions to the classical Yang Baxter equation. For a simple complex Lie group G and a Belavin-Drinfeld class, one can define a corresponding Poisson bracket on the ring of regular
functions on G. For some of these classes a compatible cluster structure can be constructed.

### Probability Semianr - No Seminar

Probability Seminar
Friday, December 2, 2016 - 2:30pm

### Jesse Berwald, Ryan Siskind: High-dimensional Retail

IMA Industrial Problems Seminar
Jesse Berwald, Ryan Siskind, Target Corporation,
Friday, December 2, 2016 - 1:25pm
##### Abstract:

For many problems encountered in industry a mathematical solution lands the user in a high dimensional space. Often the space is sparse even given terabytes of data. We discuss some approaches to these problems in the context of recently implemented products at Target.

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, December 1, 2016 - 4:40pm

### Asymptotic representation theory over Z

Colloquium
Tom Church, Stanford
Thursday, December 1, 2016 - 3:30pm
##### Abstract:

Representation theory over Z is famously intractable, but "representation stability" provides a way to get around these difficulties, at least asymptotically, by enlarging our groups until they behave more like commutative rings. Moreover, it turns out that important questions in topology/number theory/representation theory/... correspond to asking whether familiar algebraic properties hold for these "rings". I'll explain how these connections work; describe what we know and don't know; and give a wide sampling of applications in different fields where this has led to concrete results. No knowledge of representation theory will be required -- indeed, that's sort of the whole point!

### Large Time Behaviour in Fisher-KPP Type Equations

PDE Seminar
Jean-Michel Roquejoffre, University of Toulouse
Thursday, December 1, 2016 - 2:30pm
##### Abstract:

The Fisher-KPP (Kolmogorov, Petrovskii, Piskunov) equation in one space variable is one of the simplest looking reaction-diffusion equations. The solution starting from a Heaviside initial datum will converge, up to a nontrivial logarithmic time delay, to a travelling wave. This result was proved by Bramson in the early 80's, using elaborate probabilistic arguments. We will present a simple PDE proof of this result, and discuss some extensions, such as sharp asymptotics, time inhomogeneous equations, problems in several space dimensions.

Joint work with J. Nolen and L. Ryzhik.

### Algebraic Geometry Reading Group Seminar

Thursday, December 1, 2016 - 2:30pm

### New Interactions between Analysis and Number Theory

PDE Seminar
Stefan Steinerberger, Yale University
Thursday, December 1, 2016 - 1:25pm
##### Abstract:

I will discuss three different topics that connect classical analysis
with number theory in a new and unexpected way (remarks and comments
are very much appreciated!). (1) A new type of Poincare inequality on
the Torus that is optimal in all sort of ways, scales, exponents,...
and possibly suggests new families of inequalities somewhere between
elliptic estimates and dynamical systems. (2a) If the classical
Hardy-Littlewood maximal function of a function f(x) is easy to
compute, the function is f(x) = sin(x) or, equivalently, (2b) if f(x)
is periodic and the trapezoidal rule is sharp on all intervals of
length 1, then the function is trigonometric. This statement is
clearly very elementary but the only proof I could find has to use
transcendental number theory and I am not sure why! (3) Finally,
just for fun, strange, unexplained (and pretty!) patterns that appear

### Lie Theory Seminar

Lie Theory Seminar
Friday, October 7, 2016 - 3:30pm

### Afonso Bandeira: Optimality and Sub-optimality of Principal Component Analysis for Spiked Random Matrices

IMA Data Science Lab Seminar
Afonso Bandeira, Courant Institute of Mathematical Sciences
Friday, October 7, 2016 - 2:30pm
##### Abstract:

A central problem of random matrix theory is to understand the eigenvalues of spiked random matrix models, in which a prominent eigenvector (or low rank structure) is planted into a random matrix. These distributions form natural statistical models for principal component analysis (PCA) problems throughout the sciences, where the goal is often to recover or detect the planted low rank structured. In this talk we discuss fundamental limitations of statistical methods to perform these tasks and methods that outperform PCA at it. Emphasis will be given to low rank structures arising in Synchronization problems.

### Optimality and Sub-optimality of Principal Component Analysis for Spiked Random Matrices

Probability Seminar
Afonso Banderia, NYU
Friday, October 7, 2016 - 2:30pm
##### Abstract:

A central problem of random matrix theory is to understand
the eigenvalues of spiked random matrix models, in which a prominent
eigenvector (or low rank structure) is planted into a random matrix.
These distributions form natural statistical models for principal
component analysis (PCA) problems throughout the sciences, where the
goal is often to recover or detect the planted low rank structured. In
this talk we discuss fundamental limitations of statistical methods to
perform these tasks and methods that outperform PCA at it. Emphasis
will be given to low rank structures arising in Synchronization
problems.

### Collective Cell Motion in Biology

Applied and Computational Math Colloquium
Philip Maini (Ordway Lecture), Oxford University
Friday, October 7, 2016 - 2:30pm
##### Abstract:

The phenomenon of collective cell motion is widespread in biology. Cells move as individuals, as loosely signalling groups, as units in a sheet, etc. In this talk I will
review a number of applications in normal development and disease. The modelling approaches will range from partial differential equations to hybrid discrete cell-based and particular applications will cover cranial neural crest cell migration, the role of heterogeneity in cancer cell migration and epithelial sheet dynamics.

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, October 6, 2016 - 4:40pm

### Colloquium

Colloquium
Thursday, October 6, 2016 - 3:30pm

### Algebraic Geometry Reading Group Seminar

Thursday, October 6, 2016 - 2:30pm

### SIAM Student Chapter Reading Group Seminar

Thursday, October 6, 2016 - 1:25pm

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Thursday, October 6, 2016 - 1:25pm

### Should you go to graduate school? (Panel)

Math Club Seminar
Thursday, October 6, 2016 - 12:20pm
##### Abstract:

Come join us for a discussion about graduate schools. Hear from people with a variety of backgrounds discuss their experiences. Pizza and Pop as always!

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, October 6, 2016 - 11:15am

### Sectional Curvature for Riemannian Manifolds with Density

Geometric Analysis Learning Seminar
Thursday, October 6, 2016 - 11:10am

### Graeme Milton: Analytic and Polynomial Materials

IMA Annual Program
Graeme Milton, The University of Utah
Thursday, October 6, 2016 - 11:00am
##### Abstract:

The theory of inhomogeneous analytic and polynomial materials is developed. These are media where the coefficients entering the equations involve analytic functions or polynomials. Three types of analytic or polynomial materials are identified. The first two types involve an integer p. If p takes its maximum value then we have a complete analytic or polynomial material. Otherwise it is incomplete analytic or polynomial material of rank p. For two-dimensional materials further progress can be made in the identification of analytic and polynomial materials by using the well-known fact that a 90 degrees rotation applied to a divergence free field in a simply connected domain yields a curl-free field, and this can then be expressed as the gradient of a potential. Other exact results for the fields in inhomogeneous media are reviewed. Also reviewed is the subject of metamaterials, as these materials provide a way of realizing desirable coefficients in the equations.

### SIAM Student Chapter Reading Group Seminar

Thursday, October 6, 2016 - 8:30am

### Analytic torsion of manifolds with fibered cusps

PDE Seminar
Pierre Albin, University of Illinois, Urbana-Champaign
Wednesday, October 5, 2016 - 3:30pm
##### Abstract:

Analytic torsion is a spectral invariant of the Hodge Laplacian of a manifold with a flat connection. On a closed manifold it is equal to a topological invariant known as Reidemeister torsion. I will describe joint work with Frédéric Rochon and David Sher establishing a topological expression for the analytic torsion of a manifold with fibered cusp ends (such as a locally symmetric space of rank one). We establish our result by controlling the behavior of the spectrum along a degenerating class of Riemannian metrics

### Newton-Okounkov Bodies of Bott-Samelson and Peterson Varieties

Algebraic Geometry
Lauren DeDieu, University of Minnesota
Wednesday, October 5, 2016 - 2:30pm
##### Abstract:

The theory of Newton-Okounkov bodies can be viewed as a generalization of the theory of toric varieties; it associates a convex body to an arbitrary variety (equipped with auxiliary data). Although initial steps have been taken for formulating geometric situations under which the
Newton-Okounkov body is a rational polytope, there is much that is still unknown. In particular, very few concrete and explicit examples have been computed thus far. In this talk I will introduce the theory of Newton-Okounkov bodies, and will discuss the construction of Newton-Okounkov bodies of
Peterson and Bott-Samelson varieties (for certain classes of auxiliary data on these varieties). Both of these varieties arise, for instance, in the geometric study of representation
theory.

### Sang-Hyun Oh: Tutorial on Plasmonics

IMA Annual Program
Sang-Hyun Oh, University of Minnesota, Twin Cities
Wednesday, October 5, 2016 - 11:00am

### Udayan Kanade: Could a Theorem Light Our Lives?

IMA Industrial Problems Seminar
Tuesday, October 4, 2016 - 1:30pm
##### Abstract:

When faced with two objectives to maximize, engineers expect a trade-off. In the lighting industry, for example, one wishes to maximize the efficiency of a light source, and also the uniformity of its illumination. Almost all engineers will tell you, without any further thought, that there will be a trade-off between the two. Light source designers have come to live with this trade-off, and write many papers on how to measure and co-optimize these, and other measures of light sources. Enter, a new theorem. We will show that (under certain conditions) this trade-off vanishes: both uniformity and efficiency can be fully optimized. In other words, there is a light source which is as efficient as a light source can be, and as uniform as a light source can be. We will also describe our attempts at creating actual light sources using the new theory, and certain "exotic" side-effects.

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, October 4, 2016 - 1:25pm

### Climate Change Seminar

Climate Seminar
Tuesday, October 4, 2016 - 11:15am

### Approximating Functions with Singularities

Cockburn's Seminar
Monday, October 3, 2016 - 3:35pm
##### Abstract:

Title: Approximating Functions with Singularities

### Epstein zeta functions IV

Automorphic Forms and Number Theory
Monday, October 3, 2016 - 3:35pm

### An overview of equivariant stable homotopy theory and stable functor calculus

Topology Seminar
Saul Glasman, UMN
Monday, October 3, 2016 - 2:30pm
##### Abstract:

This will be an almost totally expository introduction to certain topics in stable homotopy theory. I'll attempt to motivate and introduce Elmendorf's theorem on G-spaces and the spectral Mackey functor approach to G-spectra. I'll then discuss Goodwillie's functor calculus for functors from spectra to spectra, which answers the question of what it means for such a functor to be "polynomial". If time permits, I'll start exploring the analogies between these two theories, a task which will be taken to its conclusion in next week's talk.

### Student Number Theory Seminar

Student Number Theory Seminar
Monday, October 3, 2016 - 12:20pm

### Reading Seminar for Automorphic Forms

Monday, October 3, 2016 - 9:00am

### Price Optimization in Property & Casualty Insurance

MCFAM Seminar
Rick Sutherland, FCAS, The Travelers Companies, Inc.
Friday, September 30, 2016 - 5:30pm
##### Abstract:

Price Optimization is a hot topic in the United States Property/Casualty insurance industry. Just in the past few months, the National Association of Insurance Commissioners issued a white paper, multiple states’ insurance regulators released bulletins, and the Casualty Actuarial Society added it to its Exam 6-US syllabus. The regulatory landscape is quickly changing in regards to the definition of and rules around the usage of Price Optimization in insurance. In this presentation, the speaker will provide a simple example of Price Optimization, give a brief overview of the evolution of Price Optimization discussions within the insurance industry, and discuss the recent regulatory response.

Bio: ?Rick Sutherland is a Fellow of the Casualty Actuarial Society (FCAS). He has worked at the Travelers Company, Inc. for 10 years. Currently he is a 2nd VP in the Business Insurance Product Analytics & Innovation Group within the Umbrella & Professional Lines business unit. His previous positions include: Commercial Accounts-Actuarial, Public Sector-Actuarial and Corporate-Actuarial. He graduated from St. Olaf College with a Bachelor's Degree in Mathematics.

### Mathematical Challenges Arising from Modelling in Biology

Math Biology Seminar
Friday, September 30, 2016 - 3:35pm

### Discrete Solitons in Infinite Reduced Words

Combinatorics Seminar
Friday, September 30, 2016 - 3:35pm
##### Abstract:

We consider a discrete dynamical system where the roles of the states and the carrier are played by translations in an affine Weyl group of type A. The Coxeter generators are enriched by parameters, and the interactions with the carrier are realized using Lusztig's braid move (a,b,c)?(bc/(a+c),a+c,ab/(a+c)). We use wiring diagrams on a cylinder to interpret chamber variables as ?-functions. This allows us to reduce to the discrete Kadomtsev-Petviashvili equation, and thus to obtain N-soliton solutions. This is joint work with Max Glick.

### Lie Theory Seminar

Lie Theory Seminar
Friday, September 30, 2016 - 3:30pm

### Vector diffusion maps and the graph connection Laplacian

Applied and Computational Math Colloquium
Amit Singer, Princeton University
Friday, September 30, 2016 - 2:30pm
##### Abstract:

Vector diffusion maps (VDM) is a mathematical framework for organizing and analyzing high-dimensional datasets that generalizes diffusion maps and other nonlinear dimensionality reduction methods, such as LLE, ISOMAP, and Laplacian eigenmaps. Whereas weighted undirected graphs are commonly used to describe networks and relationships between data objects, in VDM each edge is endowed with an orthogonal transformation encoding the relationship between the data at its vertices. The graph structure and orthogonal transformations are summarized by the graph connection Laplacian. In manifold learning, VDM can infer topological properties from point cloud data such as orientability, and graph connection Laplacians converge to their manifold counterparts (Laplacians for vector fields and higher order forms) in the large sample limit. The graph connection Laplacian satisfies a Cheeger-type inequality that provides a theoretical performance guarantee for the popular spectral algorithm for rotation synchronization, a problem with many applications in robotics and computer vision. The application to 2D class averaging in cryo-electron microscopy will serve as our main motivation.

### No seminar

Probability Seminar
Friday, September 30, 2016 - 2:30pm

### Amit Singer: Vector Diffusion Maps and the Graph Connection Laplacian

IMA Data Science Lab Seminar
Amit Singer, Princeton University
Friday, September 30, 2016 - 2:30pm
##### Abstract:

Vector diffusion maps (VDM) is a mathematical framework for organizing and analyzing high-dimensional datasets that generalizes diffusion maps and other nonlinear dimensionality reduction methods, such as LLE, ISOMAP, and Laplacian eigenmaps. Whereas weighted undirected graphs are commonly used to describe networks and relationships between data objects, in VDM each edge is endowed with an orthogonal transformation encoding the relationship between the data at its vertices. The graph structure and orthogonal transformations are summarized by the graph connection Laplacian. In manifold learning, VDM can infer topological properties from point cloud data such as orientability, and graph connection Laplacians converge to their manifold counterparts (Laplacians for vector fields and higher order forms) in the large sample limit. The graph connection Laplacian satisfies a Cheeger-type inequality that provides a theoretical performance guarantee for the popular spectral algorithm for rotation synchronization, a problem with many applications in robotics and computer vision. The application to 2D class averaging in cryo-electron microscopy will serve as our main motivation.

### Sang-Hyun Oh: Tutorial on Plasmonics

IMA Annual Program
Sang-Hyun Oh, University of Minnesota, Twin Cities
Friday, September 30, 2016 - 11:30am

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, September 29, 2016 - 4:40pm

### Amit Singer: The Mathematics of Cryo-electron Microscopy

IMA Data Science Lab Seminar
Amit Singer, Princeton University
Thursday, September 29, 2016 - 3:30pm
##### Abstract:

Single particle cryo-electron microscopy (EM) recently joined X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy as a high-resolution structural method for biological macromolecules. In single particle cryo-EM, the 3-D structure needs to be determined from many noisy 2-D projection images of individual, ideally identical frozen-hydrated macromolecules whose orientations and positions are random and unknown.

I will give a brief introduction to the modern computational challenges in single particle cryo-EM, focusing on 3-D ab-initio modelling, and how it can be solved using representation theory, Fourier analysis, and semidefinite programming.

### The mathematics of cryo-electron microscopy

Colloquium
Amit Singer (Ordway Lecturer), Princeton University
Thursday, September 29, 2016 - 3:30pm
##### Abstract:

Single particle cryo-electron microscopy (EM) recently joined X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy as a high-resolution structural method for biological macromolecules. In single particle cryo-EM, the 3-D structure needs to be determined from many noisy 2-D projection images of individual, ideally identical frozen-hydrated macromolecules whose orientations and positions are random and unknown. I will give a brief introduction to the modern computational challenges in single particle cryo-EM, focusing on 3-D ab-initio modelling, and how it can be solved using representation theory, Fourier analysis, and semidefinite programming.

### Algebraic Geometry Reading Group Seminar

Thursday, September 29, 2016 - 2:30pm

### Non-displaceablity of Lagrangian Submanifolds

Differential Geometry and Symplectic Topology Seminar
Kaoru Ono, Kyoto University
Thursday, September 29, 2016 - 1:25pm

### SIAM Student Chapter Reading Group Seminar

Thursday, September 29, 2016 - 1:25pm

### Math Club

Math Club Seminar
Thursday, September 29, 2016 - 12:20pm

### Free Complexes on Smooth Toric Varieties

Commutative Algebra Seminar
Christine Berkesch Zamaere, University of Minnesota
Thursday, September 29, 2016 - 11:15am
##### Abstract:

Given a module M over the Cox ring S of a smooth toric variety, one can consider free complexes that are acyclic modulo irrelevant homology, which we call a free Cox complex for M. These complexes have many advantages over minimal free resolutions over smooth toric varieties other than projective spaces. We develop this in detail for products of projective spaces. This is joint work with Daniel Erman and Gregory G. Smith

### Existence and Applications of Ricci Flows via Pseudolocality

Geometric Analysis Learning Seminar
Thursday, September 29, 2016 - 11:10am

### Stephen Shipman: Fast Computation of 2D-Periodic Green Functions in 3D Near Cutoff Frequencies

IMA Annual Program
Stephen Shipman, Louisiana State University
Thursday, September 29, 2016 - 11:00am
##### Abstract:

We present an efficient method for computing wave scattering by 2D-periodic diffraction gratings in 3D space near cutoff frequencies, at which a Rayleigh wave is at grazing incidence to the grating. At these frequencies (a.k.a. Wood-anomaly frequencies), the spatial lattice sum for the quasi-periodic Green function diverges (the Green function doesn’t even exist!). We present a modification of this lattice sum by images, which results in algebraic convergence. Away from cutoff frequencies, one can actually obtain super-algebraic convergence to the unmodified quasi-periodic Green function by smooth truncation—however, realization of this convergence rate degenerates close to cutoff and one needs to invoke images. This is joint work with O. Bruno, C. Turc, and S. Venakides.

### SIAM Student Chapter Reading Group Seminar

Thursday, September 29, 2016 - 8:30am

### Mixed Boundary Value Problem in Unbounded Domains for Elliptic equations of Second Order

PDE Seminar
Akif Ibraguimov, Texas Tech University
Wednesday, September 28, 2016 - 3:30pm
##### Abstract:

In this paper we will investigate regularity problem at infinity for solutions of elliptic equations of second order with respect to mixed Dirichlet and Neumann boundary conditions. We will show that under some assumption on Dirichlet and Neumann parts of the boundary, the solution is regular at in infinity.

First this type of test was obtained in a breakthrough work by Vladimir Mazya for elliptic equations in divergent form in "An analogue of Wiener's criterion for the Zaremba problem in a cylindrical domain." Funktsional. Anal. i Prilozhen. 16 (1982), No. 4.

In the current research both divergent and non-divergent equations will be considered. Main result for divergent equations is a part of a joint project with Alexander Grigoryan from Bielefield University. The main result for non-divergent equations is a joint project with Alexander Nazarov from St. Petersburg Department of V.A.Steklov Institute of Mathematics.

### Algebraic Geometry

Algebraic Geometry
Wednesday, September 28, 2016 - 2:30pm

### Sang-Hyun Oh: Tutorial on Plasmonics

IMA Annual Program
Sang-Hyun Oh, University of Minnesota, Twin Cities
Wednesday, September 28, 2016 - 11:00am

### Algebraic Geometry Reading Group Seminar

Wednesday, September 28, 2016 - 9:30am

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, September 27, 2016 - 1:25pm

### Amit Singer: PCA from Noisy Linearly Reduced Measurements

IMA Data Science Lab Seminar
Amit Singer, Princeton University
Tuesday, September 27, 2016 - 1:25pm
##### Abstract:

We consider the problem of estimating the covariance of X from measurements of the form y_i = A_i*x_i + e_i (for i = 1, . . . , n) where x_i are i.i.d. unobserved samples of X, A_i are given linear operators, and e_i represent noise. Our estimator is constructed efficiently via a simple linear inversion using conjugate gradient performed after eigenvalue shrinkage motivated by the spike model in high dimensional PCA. Applications to 2D image denoising, 3D ab-initio modelling, and 3D structure classification in single particle cryo-electron microscopy will be discussed.

Amit Singer is a Professor of Mathematics and member of the Executive Committee of the Program in Applied and Computational Mathematics (PACM) and of the Executive Committee for the Center for Statistics and Machine Learning (CSML) at Princeton University. He joined Princeton as an Assistant Professor in 2008. From 2005 to 2008 he was a Gibbs Assistant Professor in Applied Mathematics at the Department of Mathematics, Yale University. Singer received the BSc degree in Physics and Mathematics and the PhD degree in Applied Mathematics from Tel Aviv University (Israel), in 1997 and 2005, respectively. He served in the Israeli Defense Forces during 1997-2003. His list of awards includes a National Finalist for Blavatnik Awards for Young Scientists (2016), Moore Investigator in Data-Driven Discovery (2014), the Simons Investigator Award (2012), the Presidential Early Career Award for Scientists and Engineers (2010), the Alfred P. Sloan Research Fellowship (2010) and the Haim Nessyahu Prize for Best PhD in Mathematics in Israel (2007). His current research in applied mathematics focuses on theoretical and computational aspects of data science, and on developing computational methods for structural biology.

### Climate Change Seminar

Climate Seminar
Tuesday, September 27, 2016 - 11:15am

### Amit Singer: PCA from Noisy Linearly Reduced Measurements

IMA Industrial Problems Seminar
Tuesday, September 27, 2016 - 8:25am
##### Abstract:

Amit Singer (Princeton University) We consider the problem of estimating the covariance of X from measurements of the form y_i = A_i*x_i + e_i (for i = 1, . . . , n) where x_i are i.i.d. unobserved samples of X, A_i are given linear operators, and e_i represent noise. Our estimator is constructed efficiently via a simple linear inversion using conjugate gradient performed after eigenvalue shrinkage motivated by the spike model in high dimensional PCA. Applications to 2D image denoising, 3D ab-initio modelling, and 3D structure classification in single particle cryo-electron microscopy will be discussed. Amit Singer is a Professor of Mathematics and member of the Executive Committee of the Program in Applied and Computational Mathematics (PACM) and of the Executive Committee for the Center for Statistics and Machine Learning (CSML) at Princeton University. He joined Princeton as an Assistant Professor in 2008. From 2005 to 2008 he was a Gibbs Assistant Professor in Applied Mathematics at the Department of Mathematics, Yale University. Singer received the BSc degree in Physics and Mathematics and the PhD degree in Applied Mathematics from Tel Aviv University (Israel), in 1997 and 2005, respectively. He served in the Israeli Defense Forces during 1997-2003. His list of awards includes a National Finalist for Blavatnik Awards for Young Scientists (2016), Moore Investigator in Data-Driven Discovery (2014), the Simons Investigator Award (2012), the Presidential Early Career Award for Scientists and Engineers (2010), the Alfred P. Sloan Research Fellowship (2010) and the Haim Nessyahu Prize for Best PhD in Mathematics in Israel (2007). His current research in applied mathematics focuses on theoretical and computational aspects of data science, and on developing computational methods for structural biology.

### Approximating Functions with Singularities

Cockburn's Seminar
Monday, September 26, 2016 - 3:35pm
##### Abstract:

Title: Approximating Functions with Singularities

### Epstein zeta functions, III

Automorphic Forms and Number Theory
Monday, September 26, 2016 - 3:35pm

### Artin induction for ring spectra and algebraic K-theory

Topology Seminar
Akhil Mathew, Harvard University
Monday, September 26, 2016 - 2:30pm
##### Abstract:

A theorem of Mitchell states that the chromatic complexity of the algebraic K-theory spectrum of a discrete ring R is bounded by one, i.e., the Morava K-theory vanishes at heights at least two. We give an approach for bounding the chromatic complexity in the algebraic K-theory of ring spectra.

Let R be a ring spectrum. We say that R-based Artin induction holds for a family of groups if for every finite group G, the rationalized Grothendieck group of the category of perfect R-modules with G-action is induced from the given family. We show that Artin induction theorems can be used to bound chromatic complexity and give several examples in ring spectra, in line with the redshift philosophy of Rognes. This is joint work with Dustin Clausen, Niko Naumann, and Justin Noel.

### Student Number Theory Seminar

Student Number Theory Seminar
Monday, September 26, 2016 - 12:20pm

### Reading Seminar for Automorphic Forms

Monday, September 26, 2016 - 9:00am

### Empirical Minimum Variance Delta hedging

MCFAM Seminar
Dr. Javier Acosta, University of Minnesota School of Mathematics Alumnus- PhD Program
Friday, September 23, 2016 - 5:30pm
##### Abstract:

This presentation will review the recent paper "Optimal Delta Hedging for Options" (Hull and White, 2016). The goal of Delta-hedging is to minimize the variance of a portfolio's value change as the underlying moves. The usual Black-Scholes Delta does not accomplish this goal, as it ignores the non-zero correlation between the movement of the underlying and the implied volatility. Hull and White propose a simple method of adjusting Delta based on historical data, producing better hedging results for options on the S&P500 index.

Bio: Dr. Javier Acosta got this PhD from the University of Minnesota's School of Mathematics. His research interests include probability and game theory. Dr. Acosta works in the Quant Finance field. He has industry experience in both banking and insurance hedging.

### Evenness of Reduced Word Graphs

Combinatorics Seminar
Friday, September 23, 2016 - 3:35pm
##### Abstract:

The reduced expressions for a given element w of a Coxeter group (W, S) can be regarded as the vertices of a directed graph R(w); its arcs correspond to the braid moves. Specifically, an arc goes from a reduced expression a to a reduced expression b when b is obtained from a by replacing a contiguous subword of the form stst... (for some distinct s, t ? S) by tsts... (where both subwords have length the order of st). We prove a strong bipartiteness-type result for this graph R(w): Not only does every cycle of R(w) have even length; actually, the arcs of R(w) can be colored (with colors corresponding to the type of braid moves used), and to every color c corresponds an "opposite" color c^op (corresponding to the reverses of the braid moves with color c), and for any color c, the number of arcs in any given cycle of R(w) having color in {c, c^op} is even. This is generalizes and improves on a 2014 result by Bergeron, Ceballos and Labbé. I will also discuss some conjectures generalizing it even
further.

### Lie Theory Seminar

Lie Theory Seminar
Friday, September 23, 2016 - 3:30pm

### Applied and Computational Math Colloquium

Applied and Computational Math Colloquium
Friday, September 23, 2016 - 2:30pm

### The energy landscape of the Sherrington-Kirkpatrick model

Probability Seminar
Wei-Kuo Chen, UMN
Friday, September 23, 2016 - 2:30pm
##### Abstract:

The Sherrington-Kirkpatirck (SK) model is a mean-field spin glass introduced by theoretical physicists in order to explain the strange behavior of certain alloy, such as CuMn. Despite of its seemingly simple formulation, it was conjectured to possess a number of fruitful properties. This talk will be focused on the energy landscape of the SK model. First, we will present a formula for the maximal energy in Parisi's formulation. Second, we will give a description of the energy landscape by showing that near any given energy level between zero and maximal energy, there exist exponentially many equidistant spin configurations. Based on joint works with Auffinger, Handschy, and Lerman.

### SIAM Internship Panel

IMA Industrial Problems Seminar
-, -
Friday, September 23, 2016 - 1:25pm
##### Abstract:

The event will have graduate students speaking about their experiences with their summer internships and professors speaking about their experience facilitating internships. Following their talks, we will have a question and answer session. Food and beverages will be provided at the event. The participants of the Graduate Student Internship Panel will be: Prof. Gilad Lerman, Paula Dasbach (interned at Medtronic), Tyler Maunu (NGA), Swayambhoo Jain (interned at Yahoo), Hailee Peck (interned at Los Alamos). The event is organized by the SIAM Student Chapter at the University of Minnesota.

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, September 22, 2016 - 4:40pm

### Colloquium - TBA

Colloquium
Thursday, September 22, 2016 - 3:30pm

### Algebraic Geometry Reading Group Seminar

Thursday, September 22, 2016 - 2:30pm

### Properties of Translating Solitons

Differential Geometry and Symplectic Topology Seminar
Li Ma, Henan Normal University, China
Thursday, September 22, 2016 - 1:25pm
##### Abstract:

We discuss various properties of translating soliton hypersurfaces in R^{n+1}. We also consider their monotonicity formula, Kato inequality, and some Bernstein type results. The main material is from a joint work M. Vicente.

### SIAM Student Chapter Reading Group Seminar

Thursday, September 22, 2016 - 1:25pm

### Math Club

Math Club Seminar
Thursday, September 22, 2016 - 12:20pm

### The Sandpile Group of a Finite Group Representation

Commutative Algebra Seminar
Thursday, September 22, 2016 - 11:15am
##### Abstract:

(joint work with G. Benkart and C. Klivans; arXiv:1601.06849)

For any (finite-dimensional, faithful, complex) representation of a finite group G,
we define a new invariant, which one might call its "sandpile group". This invariant is a finite abelian group, but also has a natural commutative product: it is the augmentation ideal for a certain quotient of the commutative ring of virtual characters of G. It also bears a close relation to the McKay correspondence.

The goal in this talk will be to define this invariant, compute a few examples, and advertise an example where it is an open combinatorial challenge to compute its structure completely. It is our hope that more commutative algebraic technique might help in resolving this.

### Geometric Analysis Learning Seminar

Geometric Analysis Learning Seminar
Thursday, September 22, 2016 - 11:10am

### C. Eugene Wayne: The Derivation and Justification of Modulation Equations for Optical Systems

IMA Annual Program
C. Eugene Wayne, Boston University
Thursday, September 22, 2016 - 11:00am
##### Abstract:

“Modulation” or “Amplitude” equations are simplified equations that are believed to capture the essentials of the behavior of more complicated physical systems. Examples include the Korteweg-de Vries equation (KdV), the nonlinear Schroedinger equation (NLS) and Ginzburg-Landau equation. They arise in many different physical contexts and serve as prototypical examples or “normal forms” for a variety of nonlinear phenomena. This talk will focus on the derivation of the NLS equation as an approximation to describe the propagation of pulses in nonlinear optical fibers and will also discuss how one can derive rigorous estimates for the difference between the approximation given by the NLS equation and the true solution of the more complicated physical system. If time permits I will also discuss possible modulation equations for regimes in which the NLS approximation breaks down.

### SIAM Student Chapter Reading Group Seminar

Thursday, September 22, 2016 - 8:30am

### Poisson stochastic Process and Basic Schauder and Sobolev-Space Estimates in the Theory of Parabolic Equations

PDE Seminar
Nicolai Krylov, University of Minnesota
Wednesday, September 21, 2016 - 3:30pm
##### Abstract:

We show how knowing Schauder and Sobolev-space estimates for the one-dimensional heat equation allows one to derive their multidimensional analogs for equations with coefficients depending only on time variable with the SAME constants as in the case of the one-dimensional heat equation. The method is based on using the Poisson stochastic process. It looks like no other method is available at this time and it is a very challenging problem to find a purely analytic approach to proving such results. Joint work with E. Priola.

### New Relations on Caporaso-Harris Invariants and More

Algebraic Geometry
Wednesday, September 21, 2016 - 2:30pm
##### Abstract:

Caporaso-Harris invariants count the number of nodal curves on theprojective plane satisfying given tangency conditions with a line. Those invariants are first proved to satisfy a recursive formula in1996 and then showed to be polynomials in the degree (when the degreeis large enough) using tropical geometry in 2009. On the other hand, the number of nodal curves are already known to be universal polynomials of the Chern numbers for any surfaces and line bundles. Inthis talk we will discuss a new type of relations for Caporaso-Harrisinvariants which unify these features and in fact also hold on all smooth varieties.

### Algebraic Geometry Reading Group Seminar

Wednesday, September 21, 2016 - 9:30am

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, September 20, 2016 - 1:25pm

### Xiuyuan Cheng: Limiting Spectrum of Random Kernel Matrices

IMA Data Science Lab Seminar
Xiuyuan Cheng, Yale University
Tuesday, September 20, 2016 - 1:25pm
##### Abstract:

We consider n-by-n matrices whose (i, j)-th entry is f(X_i^T X_j), where X_1, ...,X_n are i.i.d. standard Gaussian random vectors in R^p, and f is a real-valued function. The eigenvalue distribution of these kernel random matrices is studied in the "large p, large n" regime. It is shown that with suitable normalization the spectral density converges weakly, and we identify the limit. Our analysis applies as long as the rescaled kernel function is generic, and particularly, this includes non-smooth functions, e.g. Heaviside step function. The limiting densities "interpolate" between the Marcenko-Pastur density and the semi-circle density.

Xiuyuan Cheng is currently a Gibbs Assistant Professor at the Program of Applied Mathematics of Yale University. Before joining Yale, she was a Postdoctoral Researcher in Département d'Informatique of École normale supérieure, France, from 2013 to 2015. She received her Ph.D. from the Program of Applied and Computational Mathematics at Princeton University in 2013, advised jointly by Prof. Amit Singer and Prof. Weinan E. Her research focuses on high dimensional data analysis and mathematical theories of machine learning.

### Climate Change Seminar

Climate Seminar
Richard McGehee, University of Minnesota, School of Mathematics
Tuesday, September 20, 2016 - 11:15am
##### Abstract:

An Introduction to Budyko's Equation

### Epstein zeta functions, II

Automorphic Forms and Number Theory
Monday, September 19, 2016 - 3:35pm

### Approximating Functions with Singularities

Cockburn's Seminar
Monday, September 19, 2016 - 3:35pm
##### Abstract:

Title: Approximating Functions with Singularities

### Topology Seminar

Topology Seminar
Monday, September 19, 2016 - 2:30pm

### Student Number Theory Seminar

Student Number Theory Seminar
Monday, September 19, 2016 - 12:20pm
##### Abstract:

Title: A Crash Course in Lie Theory and Reductive Groups

Abstract: Reductive groups such as GL(n), O(n), and Sp(n) are ubiquitous in modern mathematics. The structure theory of such groups (over a smorgasbord of fields) is well understood yet quite verbose, which can make a large swath of mathematics impenetrable to the uninitiated. I will introduce some of the "major players" in the study of reductive groups, emphasizing examples and intuition to help orient a newcomer to the field. In particular, I hope to

explain what a reductive group is
discuss the Lie algebra of a reductive group
introduce important subgroups (or subalgebras) of these groups (or Lie algebras), and
state/allude to the finite type classification of semisimple Lie algebras.

This talk is geared towards first and second year graduate students who have not yet taken Lie Groups and Lie Algebras.

### Reading Seminar for Automorphic Forms

Monday, September 19, 2016 - 9:00am

### MFM Alumni/Current Student Panel

MCFAM Seminar
Panel of various MFM alumni and 2nd year MFM Students, MFM - University of Minnesota's MCFAM
Friday, September 16, 2016 - 5:30pm
##### Abstract:

A variety of local quantitive analysts, investment analysts who are alumni of the MFM and 2nd year MFM students will talk to the incoming MFM class and other interested students and individuals about: (1) what they learned in the MFM, (2) what helped them find internships and jobs and (3) the most important things to do to take advantage of all during your time in the program: academics, program activiites as well as related opportunities in town and across the country/globe to learn more about the field of Quantitative Finance

### The Greedy Basis Equals the Theta Basis: A Rank Two Haiku

Combinatorics Seminar
Gregg Musiker, School of Mathematic - University of Minnesota
Friday, September 16, 2016 - 3:35pm
##### Abstract:

In groundbreaking work from a few years ago, K. Lee, L. Li, and A. Zelevinsky constructed a basis for any rank 2 cluster algebra that consists of a special family of indecomposable positive elements. They coined the term Greedy Basis for this construction and illustrated a combinatorial interpretation of the Laurent expansions of its elements using Dyck paths. Ensuing work by M. Gross, P. Hacking, S. Keel, and M. Kontsevich used algebraic geometry, as inspired by mirror symmetry and tropical geometry, to define the Theta Basis for any cluster algebra. The construction of the theta basis can be described in terms of the machinery of broken lines and scattering diagrams.

In this talk, these two bases will be constructed, assuming no prior knowledge, and compared. In particular, I will discuss joint work with M. Cheung, M. Gross, G. Muller, D. Rupel, S. Stella, and H. Williams started at an AMS Mathematical Research Community, in which we equate these two bases in the rank two case. This talk will be accessible for graduate students and advanced undergraduates.

### Lie Theory Seminar

Lie Theory Seminar
Friday, September 16, 2016 - 3:30pm

### Unraveling Kidney Physiology, Pathophysiology and Therapeutics: A Modeling Approach

Applied and Computational Math Colloquium
Anita Layton, Duke University
Friday, September 16, 2016 - 2:30pm
##### Abstract:

The kidney not only filters metabolic wastes and toxins from the body,but it also regulates the body's water balance, electrolyte balance, and acid-base balance, blood pressure, and blood flow. Despite intense research, aspects of kidney functions remain incompletely understood. I will discuss how our group use mathematical modeling techniques to address a host of previously unanswered questions in renal physiology and pathophysiology: Why is the mammalian kidney so susceptible to hypoxia, despite receiving ~25% of the cardiac output? What are the mechanisms underlying the development of acute kidney injury in a patient who has undergone cardiac surgery performed on cardiopulmonary bypass? What is the effect of inhibiting sodium-glucose transport, a novel treatment for reducing renal glucose update in diabetes, on renal NaCl transport and oxygen consumption?

### Algebraically inspired results on convex functions

Probability Seminar
Liran Rotem, UMN
Friday, September 16, 2016 - 2:30pm
##### Abstract:

In this talk we will discuss new identities and constructions involving convex functions. These results demonstrate surprising formal similarities between the Legendre transform and the inversion map (say on positive real numbers). In this sense, these results are "algebraically motivated". As corollaries we will discuss decompositions of the Gaussian function, as well as a Blaschke-Santaló type result involving the Gaussian measure.

### Student Combinatorics Seminar

Student Combinatorics Seminar
Thursday, September 15, 2016 - 4:40pm

### Colloquium - TBA

Colloquium
Thursday, September 15, 2016 - 3:30pm

### Algebraic Geometry Reading Group Seminar

Thursday, September 15, 2016 - 2:30pm

### SIAM Student Chapter Reading Group Seminar

Thursday, September 15, 2016 - 1:25pm

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Thursday, September 15, 2016 - 1:25pm

### Math Club

Math Club Seminar
Thursday, September 15, 2016 - 12:20pm

### Multiplicative structures on minimal free resolutions of monomial ideals

Commutative Algebra Seminar
Lukas Katthaen, Frankfurt
Thursday, September 15, 2016 - 11:15am
##### Abstract:

The minimal free resolution of a quotient of the polynomial ring admits a (generally non-associative) multiplication which satisfies the Leibniz rule. This multiplication is far from being unique and in favorable cases it can be chosen to be associative, which makes the resolution into a DGA. In this talk, I consider these multiplicative structures in the setting of monomial ideals. On the one hand, I will present some structure theorems about these multiplications, in particular in the associative case. On the other hand, I will show that the presence of an associative multiplication has implications on the possible Betti numbers of the ideal.

### Geometric Analysis Learning Seminar

Geometric Analysis Learning Seminar
Thursday, September 15, 2016 - 11:10am

### SIAM Student Chapter Reading Group Seminar

Thursday, September 15, 2016 - 8:30am

### PDE Seminar - Spreading fronts in the anisotropic Allen-Cahn equations on R^n

PDE Seminar
Mitsunori Nara, Iwate University, Japan
Wednesday, September 14, 2016 - 3:30pm
##### Abstract:

We consider the Cauchy problem for the anisotropic Allen-Cahn equation on R^n with n\geq 2, and analyze the large time behavior of the solutions with spreading fronts. Our result states that, under some mild assumptions on
the initial value, the solution develops a well-formed front whose position roughly coincides with the spreading Wulff shape. This is a joint work with Hiroshi Matano in University of Tokyo and Yoichiro Mori in University of Minnesota.

### Algebraic Geometry Seminar

Algebraic Geometry
Wednesday, September 14, 2016 - 2:30pm

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, September 13, 2016 - 1:25pm

### Climate Change Seminar

Climate Seminar
Richard McGehee, University of Minnesota, School of Mathematics
Tuesday, September 13, 2016 - 11:15am
##### Abstract:

An Introduction to Energy Balance

### Epstein zeta functions and their zeros

Automorphic Forms and Number Theory
Monday, September 12, 2016 - 3:35pm

### Approximating Functions with Singularities

Cockburn's Seminar
Monday, September 12, 2016 - 3:35pm
##### Abstract:

Title: Approximating Functions with Singularities

### Topology Seminar

Topology Seminar
Monday, September 12, 2016 - 2:30pm

### Student Number Theory Seminar

Student Number Theory Seminar
Monday, September 12, 2016 - 12:20pm

### Reading Seminar for Automorphic Forms

Monday, September 12, 2016 - 9:00am

### Matrix Ball construction for affine Robinson-Schensted correspondence

Combinatorics Seminar
Michael Chmutov, UMN
Friday, September 9, 2016 - 3:35pm
##### Abstract:

In his study of Kazhdan-Lusztig cells in affine type A, Shi
has introduced an affine analog of Robinson-Schensted correspondence.
We generalize the Matrix-Ball Construction of Viennot and Fulton to
give a more combinatorial realization of Shi's algorithm. As a
byproduct, we also give a way to realize the affine correspondence via
the usual Robinson-Schensted bumping algorithm. Next, inspired by
Honeywill, we extend the algorithm to a bijection between the extended
affine symmetric group and collection of triples (P,Q,r) where
P and Q are tabloids and r is a dominant weight.

### Boaz Nadler: Unsupervised Ensemble Learning

IMA Data Science Lab Seminar
Boaz Nadler, Weizmann Institute of Science
Friday, September 9, 2016 - 2:30pm
##### Abstract:

In various applications, one is given the advice or predictions of several classifiers of unknown reliability, over multiple questions or queries. This scenario is different from standard supervised learning where classifier accuracy can be assessed from available labeled training or validation data, and raises several questions: Given only the predictions of several classifiers of unknown accuracies, over a large set of unlabeled test data, is it possible to
a) reliably rank them, and
b) construct a meta-classifier more accurate than any individual classifier in the ensemble?

In this talk we'll show that under various independence assumptions between
classifier errors, this high dimensional data hides simple low dimensional
structures. Exploiting these, we will present simple spectral methods to address
the above questions, and derive new unsupervised spectral meta-learners.
We'll prove these methods are asymptotically consistent when
the model assumptions hold, and present their empirical success on a variety
of unsupervised learning problems.

### Unsupervised Ensemble Learning

Applied and Computational Math Colloquium
Friday, September 9, 2016 - 2:30pm
##### Abstract:

Speaker:Boaz Nadler / Weizmann Institute of Science, Israel

Abstract:
In various applications, one is given the advice or predictions of several classifiers of unknown reliability, over multiple questions or queries. This scenario is different from standard supervised learning where classifier accuracy can be assessed from available labeled training or validation data,
and raises several questions. Given only the predictions of several classifiers of unknown accuracies, over a large set of unlabeled test data, is it possible to:
a) reliably rank them, and
b) construct a meta-classifier more accurate than any
individual classifier in the ensemble?

In this talk we'll show that under various independence assumptions between classifier errors, this high dimensional data hides simple low dimensional structures. Exploiting these, we will present simple spectral methods to address the above questions, and derive new unsupervised spectral meta-learners.

We'll prove these methods are asymptotically consistent when
the model assumptions hold, and present their empirical success on a variety of unsupervised learning problems.

### Parabolic Harnack inequalities and Poincare inequalities on Dirichlet spaces

Probability Seminar
Janna Lierl, University of Illinois at Urbana-Champaign
Friday, September 9, 2016 - 2:30pm
##### Abstract:

This talk will discuss old and new results on parabolic Harnack inequalities and Poincare inequalities on metric measure Dirichlet spaces with a doubling measure. For the case of Riemannian manifolds, it is known from the works of Grigor'yan and Saloff-Coste that the Harnack inequality is equivalent to two-sided Gaussian heat kernel estimates, as well as to the Poincare inequality together with the volume doubling property. Subsequent work by Sturm has then opened the door to related equivalence results on Dirichlet spaces. The focus of this talk will be on the case of non-symmetric operators, fractal-type spaces, as well as on relaxing the requirement that the metric be geodesic. Time permitting, I may also present estimates for non-symmetric heat kernels on fractal spaces.

### MCFAM Seminar

MCFAM Seminar
Friday, September 9, 2016 - 12:30pm

### Colloquium

Colloquium
Thursday, September 8, 2016 - 3:30pm

### SIAM Student Chapter Reading Group Seminar

Thursday, September 8, 2016 - 1:25pm

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Thursday, September 8, 2016 - 1:25pm

### Math Club

Math Club Seminar
Thursday, September 8, 2016 - 12:20pm

### Commutative Algebra Seminar

Commutative Algebra Seminar
Thursday, September 8, 2016 - 11:15am

### Geometric Analysis Learning Seminar

Geometric Analysis Learning Seminar
Thursday, September 8, 2016 - 11:10am

### SIAM Student Chapter Reading Group Seminar

Thursday, September 8, 2016 - 8:30am

### PDE Seminar

PDE Seminar
Wednesday, September 7, 2016 - 3:30pm

### Algebraic Geometry Reading Group Seminar

Algebraic Geometry
Wednesday, September 7, 2016 - 2:30pm

### Differential Geometry and Symplectic Topology seminar

Differential Geometry and Symplectic Topology Seminar
Tuesday, September 6, 2016 - 1:25pm

### Automorphic Forms and Number Theory [will not meet today]

Automorphic Forms and Number Theory
Monday, September 5, 2016 - 3:35pm