Seminars Sorted by Series

Members’ Colloquium

Nov
15
2021

Members’ Colloquium

Growth of cohomology in towers of manifolds: a topological application of the Langlands program
2:00pm|Simonyi Hall 101 and Remote Access

How does the dimension of the first cohomology grow in a tower of covering spaces? After a tour of examples of behaviors for low-dimensional spaces, I will focus on arithmetic manifolds. Specifically, for towers of complex hyperbolic manifolds, I...

Nov
22
2021

Members’ Colloquium

Mathematical foundations for human-level intelligence (Part 1): Cooperative communication as belief transport
2:00pm|Simonyi Hall 101 and Remote Access

Human learning outstrips modern machine learning and AI in at least three abilities: rapid robust learning, in effectively open worlds, in near-real time with very little energy. Mathematical formalization of signature human abilities has the...

Nov
29
2021

Members’ Colloquium

Fluid equations: regularity and Kolmogorov’s turbulence theory
2:00pm|Simonyi Hall 101 and Remote Access

The regularity theory for the Navier-Stokes equation will be reviewed. Motivations from Kolmogorov’s phenomenological theory of turbulence will be discussed. Rigorous mathematical results are obtained to confirm some of the phenomenologies.

Dec
06
2021

Members’ Colloquium

Old and New Results on the Spread of the Spectrum of a Graph
2:00pm|Simonyi Hall 101 and Remote Access

The spread of a matrix is defined as the diameter of its spectrum. This quantity has been well-studied for general matrices and has recently grown in popularity for the specific case of the adjacency matrix of a graph. Most notably, Gregory...

Dec
13
2021

Members’ Colloquium

A new random model for the Euler and Navier-Stokes equations and related equations
2:00pm|Simonyi Hall 101 and Remote Access

I will introduce a new model of randomly agitated equations. I will focus on the finite finite dimensional approximations (analogous to Galerkin approximations) and the two-dimensional setting. I will discuss number of properties of the models...

Jan
24
2022

Members’ Colloquium

Cubic surfaces and non-Euclidean geometry
2:00pm|Simonyi Hall 101 and Remote Access

The classification of geometric structures on manifolds naturally leads to actions of automorphism groups, (such as mapping class groups of surfaces) on "character varieties" (spaces of equivalence classes of representations of surface groups).

Jus...

Jan
31
2022

Members’ Colloquium

A mathematical approach to some problems in neurobiology
2:00pm|Simonyi Hall 101 and Remote Access

I will discuss some questions of interest in neuroscience, seen through the lens of mathematics. No prior knowledge of neuroscience is needed for this talk. Two of the most basic visual capabilities of primates are orientation selectivity, i.e., the...

Feb
07
2022

Members’ Colloquium

PDEs vs. Geometry: analytic characterizations of geometric properties of sets
2:00pm|Simonyi Hall 101 and Remote Access

In this talk we will discuss connections between the geometric and analytic/PDE properties of sets. The emphasis is on quantifiable, global results which yield true equivalence between the geometric and PDE notions in very rough scenarios, including...

Feb
14
2022

Members’ Colloquium

Morrey's conjecture
2:00pm|Simonyi Hall 101 and Remote Access

Morrey’s conjecture arose from a rather innocent looking question in 1952: is there a local condition characterizing "ellipticity” in the calculus of variations? Morrey was not able to answer the question, and indeed, it took 40 years until first...

Feb
28
2022

Members’ Colloquium

A Gentle Approach to Crystalline Cohomology
2:00pm|Simonyi Hall 101 and Remote Access

Let X be a smooth affine algebraic variety over the field C of complex numbers (that is, a smooth submanifold of C^n which can be described as the solutions to a system of polynomial equations). Grothendieck showed that the de Rham cohomology of X...

Mar
07
2022

Members’ Colloquium

The orbit method, microlocal analysis and applications to L-functions
2:00pm|Simonyi Hall 101 and Remote Access

I will describe how the orbit method can be developed in a quantitative form, along the lines of microlocal analysis, and applied to local problems in representation theory and global problems involving the analysis of automorphic forms. This talk...

Mar
21
2022

Members’ Colloquium

On the unpredictability of fluid motions
2:00pm|Simonyi Hall 101 and Remote Access

The fundamental equations of fluid dynamics exhibit non-uniqueness. Is this a mathematical fluke, or do the equations fail to uniquely predict the motion of fluids? In this colloquium, we present recent mathematical and physical progress toward...

May
16
2022

Members’ Colloquium

Thresholds
2:00pm|Simonyi Hall 101 and Remote Access

Thresholds for increasing properties of random structures are a central concern in probabilistic combinatorics and related areas.  In 2006, Kahn and Kalai conjectured that for any nontrivial increasing property on a finite set, its threshold is...

Members’ Seminar

Dec
06
2004

Members’ Seminar

Completing the Bernstein Program (A Geometric Conjecture within the Representation Theory of p-adic Groups)
4:00pm|S-101
Jan
31
2005

Members’ Seminar

Approximation algorithms and Grothendieck type inequalities
4:00pm|S-101

I will describe a connection between a classical inequality of Grothendieck and approximation algorithms based on semi-definite programming. The investigation of this connection suggests the definition of a new graph parameter, called the...

Feb
14
2005

Members’ Seminar

Blow up in a 3-D "toy" model for the Euler equations
4:00pm|S-101

We present a 3-D vector dyadic model given in terms of an infinite system of nonlinearly coupled ODE. This toy model is inspired by approximations to the fluid equations studied by Dinaburg and Sinai. The model has structural similarities with the...

Feb
22
2005

Members’ Seminar

A New Characterization of Sobolev Spaces
3:00pm|S-101

This talk is motivated by some recent work of Bourgain- rezis-Mironescu. A few years ago, they introduced an elementary way of defining the Sobolev spaces $W^{1,p}$ without making any use of derivatives. I will present their definition and some...

Mar
14
2005

Members’ Seminar

A Liouville Type Result for some Conformally Invariant Fully Nonlinear Equations
4:00pm|S-101

I will talk about some joint work with Yanyan Li which extended the Liouville type theorem of Caffarelli-Gidas-Spruck's on the Yamabe equation to the fully nonlinear case.

Mar
21
2005

Members’ Seminar

Polynomiality Properties of Type A Weight and Tensor Product Multiplicities
4:00pm|S-101

Kostka numbers and Littlewood-Richardson coefficients appear in the representation theory of complex semisimple Lie algebras of type A, respectively as the multiplicities of weights in irreducible representations, and the multiplicities of...

Mar
28
2005

Members’ Seminar

Exotic Smooth Structures on Rational Surfaces
4:00pm|S-101

Most known smoothable simply connected 4--manifolds admit infinitely many different smooth structures (distinguished, for example, by Seiberg--Witten invariants). There are some 4--manifolds, though, for which the existence of such 'exotic'...

Apr
11
2005

Members’ Seminar

Iterated Integrals and Algebraic Cycles
4:00pm|S-101

It will be on some constructions in the candidate category of mixed Tate Motives constructed by Bloch and Kriz.

Oct
31
2005

Members’ Seminar

Motivic Integration, Constructible Functions, and Stringy Chern Classes
4:00pm|S-101

In this talk I will discuss a joint work with Lupercio, Nevins and Uribe, in which we use motivic integration to give a theory of Chern classes for singular algebraic varieties that is birationally well-behaved (i.e., with a "stringy" flavor). The...

Nov
07
2005

Members’ Seminar

On some Properties of the Nottingham Group
4:00pm|S-101

Let F be a finite field. The Nottingham group N(F) is the group of formal power series \{ t(1+a_1 t + a_2 t^2 + ...): a_i \in F \}or, equivalently, the group of wild automorohisms of the local field F((t)). In spite of such a simple definition, the...

Nov
28
2005

Members’ Seminar

Generalized Teichmueller Spaces
4:00pm|S-101

Classical Teichmueller space parametrizes complex structures on a Riemann surface of genus g>1. Recently several generalized Teichmueller spaces have been defined and studied by very different approaches. Nevertheless, some of the results are...

Jan
30
2006

Members’ Seminar

Universality for Mathematical and Physical Systems
Percy Deift
4:00pm|S-101

All physical systems in equilibrium obey the laws of thermodynamics. In other words, whatever the precise nature of the interaction between the atoms and molecules at the microscopic level, at the macroscopic level, physical systems exhibit...

Feb
13
2006

Members’ Seminar

Random Walks and Equidistribution on Lie Groups
4:00pm|S-101

I will discuss various issues related to the local problem on Lie groups, the asymptotics of the return probablity, and the equidistribution of dense subgroups.

Feb
20
2006

Members’ Seminar

The Deligne-Simpson Problem and Double Affine Hecke Algebras
4:00pm|S-101

Let us fix $m$ conjugacy classes $C_1,\dots,C_m$ inside $GL(n)$. The variety of $m$-tuple of matrices such that: $$X_i\in C_i, \quad i=1,\dots,m mbox{ and } X_1\dots X_m=1.$$ is a solution of the Deligne-Simpson problem. Double affine Hecke algebras...

Mar
13
2006

Members’ Seminar

Multivariable Mahler Measure and Regulators
4:00pm|S-101

The Mahler measure of an n-variable polynomial P is the integral of log|P| over the n-dimensional unit torus T^n with the Haar measure. For one-variable polynomials, this is a natural quantity that appears in different problems such as Lehmer's...

Mar
27
2006

Members’ Seminar

Counting Polynomial Configurations on Dense Subsets of the Integers
4:00pm|S-101

The polynomial Szemeredi theorem of Bergelson and Leibman states that every integer subset with positive density contains infinitely many configurations of the form x,x+p_1(n),...x+p_k(n), where p_1,...,p_k is any fixed family of integer polynomials...

Apr
03
2006

Members’ Seminar

Generation of Finite Simple Groups and Derangements
4:00pm|S-101

We will first discuss some results on generation of finite simple groups. Using the classification of finite simple grouops, one can prove the following results: Every finite simple can be generated by two elements and the probability that a pair of...

Apr
10
2006

Members’ Seminar

String Topology and Closed Geodesics
4:00pm|S-101

Expository talk on work in progress. M.Chas and D.Sullivan introduced a product on the homology of the free loop spaace of a compact, oriented manifold M that has also been studied by R.L.Cohen, V.Godin, J.D.S.Jones, J.Klein, and others. If M is...

Apr
17
2006

Members’ Seminar

Fake Projective Spaces
4:00pm|S-101

A fake projective space is a smooth complex projective algebraic variety which is uniformized by the unit ball in $\mathbb C^n$ and whose Betti numbers are the same as that of $\mathbb P^n_{\mathbb{C}}$. The first example of a fake projective plane...

Apr
24
2006

Members’ Seminar

Some Results on Complete Symmetric Varieties
4:00pm|S-101

Let G be a semisimple adjoint group. There is a partition of its wonderful compactification into finitely many G-stable pieces, which was introduced by Lusztig. Each piece is a locally trivial fibration over a partial flag variety with fibres...

Oct
02
2006

Members’ Seminar

On the p-Adic Spectra of Some Hecke Operators
4:00pm|S-101

I'll first summarize my conjecture about the p-adic slopes of modular forms for GL_2 (both classical and overconvergent). This conjecture is based upon some structures in the geometry of the special fibers of elliptic modular curves at p. In an...

Oct
23
2006

Members’ Seminar

Open Gromov-Witten Theory of the Quintic Threefold
4:00pm|S-101

Recently, I defined an open Gromov-Witten invariant for Lagrangian submanifolds that arise as the real points of a real symplectic manifold. In this talk, I will discuss a calculation of the genus zero open Gromov-Witten theory of the Fermat type...

Nov
06
2006

Members’ Seminar

Equidistribution Problems on Siegel Modular Varieties
4:00pm|S-101

In this talk, I'd like to discuss an intriguing equidistribution property of automorphic forms on arithmetic quotients of homogeneous varieties, focusing on cuspidal Hecke eigenforms for Sp(n, Z), the Siegel modular group of genus n. Our approach is...

Nov
13
2006

Members’ Seminar

Random Geometry and SLE
4:00pm|S-101

We introduce and construct the "AC geometry" from the Gaussian free field and use it to prove various facts about Schramm-Loewner evolutions. 

Nov
15
2006

Members’ Seminar

Random Geometry and SLE II
2:30pm|S-101

We introduce and construct the "AC geometry" from the Gaussian free field and use it to prove various facts about Schramm-Loewner evolutions.