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Mathematics Colloquium

All colloquia are on Fridays at 4:00 pm in Van Vleck B239, unless otherwise indicated.

Spring 2016

date speaker title host(s)
January 22
January 28 (Th 4pm VV901) Steven Sivek (Princeton) The augmentation category of a Legendrian knot Ellenberg
January 29 Ana Caraiani (Princeton) Locally symmetric spaces, torsion classes, and the geometry of period domains Ellenberg
February 5 Takis Souganidis (University of Chicago) Scalar Conservation Laws with Rough Dependence Lin
February 12 Gautam Iyer (CMU) Homogenization and Anomalous Diffusion Jean-Luc
February 19 Jean-François Lafont (Ohio State) Dymarz
February 26 Hiroyoshi Mitake (Hiroshima university) Tran
March 4 Guillaume Bal (Columbia University) Li, Jin
March 11 Mitchell Luskin (University of Minnesota) Mathematical Modeling of Incommensurate 2D Materials Li
March 18 Ralf Spatzier (University of Michigan) TBA Dymarz
March 25 Spring Break
April 1 Chuu-Lian Terng (UC Irvine) --> TBA --> Mari-Beffa
April 8 Alexandru Ionescu (Princeton) TBA Wainger/Seeger
April 15 Igor Wigman (King's College - London) Nodal Domains of Eigenfunctions Gurevich/Marshall
April 22 Paul Bourgade (NYU) TBA Seppalainen/Valko
April 29 Randall Kamien (U Penn) TBA Spagnolie
May 6 Julius Shaneson (University of Pennsylvania) TBA Maxim/Kjuchukova


January 28: Steven Sivek (Princeton)

Title: The augmentation category of a Legendrian knot

Abstract: A well-known principle in symplectic geometry says that information about the smooth structure on a manifold should be captured by the symplectic geometry of its cotangent bundle. One prominent example of this is Nadler and Zaslow's microlocalization correspondence, an equivalence between a category of constructible sheaves on a manifold and a symplectic invariant of its cotangent bundle called the Fukaya category.

The goal of this talk is to describe a model for a relative version of this story in the simplest case, corresponding to Legendrian knots in the standard contact 3-space. This construction, called the augmentation category, is a powerful invariant which is defined in terms of holomorphic curves but can also be described combinatorially. I will describe some interesting properties of this category and relate it to a category of sheaves on the plane. This is joint work with Lenny Ng, Dan Rutherford, Vivek Shende, and Eric Maslow.

January 29: Ana Caraiani (Princeton)

Title: Locally symmetric spaces, torsion classes, and the geometry of period domains

Abstract: The Langlands program is an intricate network of conjectures, which are meant to connect different areas of mathematics, such as number theory, harmonic analysis and representation theory. One striking consequence of the Langlands program is the Ramanujan conjecture, which is a statement purely within harmonic analysis, about the growth rate of Fourier coefficients of modular forms. It turns out to be intimately connected to the Weil conjectures, a statement about the cohomology of projective, smooth varieties defined over finite fields.

I will explain this connection and then move towards a mod p analogue of these ideas. More precisely, I will explain a strategy for understanding torsion occurring in the cohomology of locally symmetric spaces and how to detect which degrees torsion will contribute to. The main theorem is joint work with Peter Scholze and relies on a p-adic version of Hodge theory and on recent developments in p-adic geometry.

February 5: Takis Souganidis (University of Chicago)

Title: Scalar Conservation Laws with Rough Dependence

I will present a recently developed theory for scalar conservation laws with nonlinear multiplicative rough signal dependence. I will describe the difficulties, introduce the notion of pathwise entropy/kinetic solution and its well-posedness. I will also talk about the long time behavior of the solutions as well as some regularization by noise type results.

February 12: Gautam Iyer (CMU)

Homogenization is a well known technique used to approximate the macroscopic behaviour of a material with microscopic impurities. While this originally arose in the study of composite materials, it has applications to various other fields, and I will focus on a few results motivated by fluid dynamics. One well known result in this direction is by GI Taylor estimating the dispersion rate of a solute in a pipe. The length scales involved in typical pipelines, however, are too short for this result to apply. I will conclude with a few recent "intermediate time" results describing the effective behaviour in scaling regimes outside those of standard homogenization results.

March 11: Mitchell Luskin (UMN)

Title: Mathematical Modeling of Incommensurate 2D Materials

Abstract: Incommensurate materials are found in crystals, liquid crystals, and quasi-crystals. Stacking a few layers of 2D materials such as graphene and molybdenum disulfide, for example, opens the possibility to tune the elastic, electronic, and optical properties of these materials. One of the main issues encountered in the mathematical modeling of layered 2D materials is that lattice mismatch and rotations between the layers destroys the periodic character of the system. This leads to complex commensurate-incommensurate transitions and pattern formation.

Even basic concepts like the Cauchy-Born strain energy density, the electronic density of states, and the Kubo-Greenwood formulas for transport properties have not been given a rigorous analysis in the incommensurate setting. New approximate approaches will be discussed and the validity and efficiency of these approximations will be examined from mathematical and numerical analysis perspectives.

Past Colloquia

Fall 2015

Spring 2015

Fall 2014

Spring 2014

Fall 2013

Spring 2013

Fall 2012