Seminars and Colloquia by Series

Monotone generative modeling via a geometry-preserving mapping

Series
Applied and Computational Mathematics Seminar
Time
Monday, April 15, 2024 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005 and https://gatech.zoom.us/j/98355006347
Speaker
Wonjun LeeUniversity of Minnesota, Twin Cities

Generative Adversarial Networks (GANs) are powerful tools for creating new content, but they face challenges such as sensitivity to starting conditions and mode collapse. To address these issues, we propose a deep generative model that utilizes the Gromov-Monge embedding (GME). It helps identify the low-dimensional structure of the underlying measure of the data and then map it, while preserving its geometry, into a measure in a low-dimensional latent space, which is then optimally transported to the reference measure. We guarantee the preservation of the underlying geometry by the GME and c-cyclical monotonicity of the generative map, where c is an intrinsic embedding cost employed by the GME. The latter property is a first step in guaranteeing better robustness to initialization of parameters and mode collapse. Numerical experiments demonstrate the effectiveness of our approach in generating high-quality images, avoiding mode collapse, and exhibiting robustness to different starting conditions.

Eremenko’s Conjecture and Wandering Lakes of Wada

Series
CDSNS Colloquium
Time
Friday, April 12, 2024 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 254
Speaker
James WatermanStonybrook University

In 1989, Eremenko investigated the set of points that escape to infinity under iteration of a transcendental entire function, the so-called escaping set. He proved that every component of the closure of the escaping set is unbounded and conjectured that all the components of the escaping set are unbounded. Much of the recent work on the iteration of entire functions is involved in investigating properties of the escaping set, motivated by Eremenko's conjecture. We will begin by introducing many of the basic dynamical properties of iterates of an analytic function, and finally discuss constructing a transcendental entire function with a point connected component of the escaping set, providing a counterexample to Eremenko's conjecture. This is joint work with David Martí-Pete and Lasse Rempe.

Enumeration of interval graphs and d-representable complexes (Amzi Jeffs, CMU)

Series
Combinatorics Seminar
Time
Friday, April 12, 2024 - 15:15 for 1 hour (actually 50 minutes)
Location
Speaker
Amzi JeffsCarnegie Mellon University

How many different ways can we arrange n convex sets in R^d? One answer is provided by counting the number of d-representable complexes on vertex set [n]. We show that there are exp(Theta(n^d log n))-many such complexes, and provide bounds on the constants involved. As a consequence, we show that d-representable complexes comprise a vanishingly small fraction of the class of d-collapsible complexes. In the case d = 1 our results are more precise, and improve the previous best estimate for the number of interval graphs.

Riemannian geometry and contact topology IV

Series
Geometry Topology Working Seminar
Time
Friday, April 12, 2024 - 14:00 for 2 hours
Location
Skiles 006
Speaker
John EtnyreGeorgia Tech

This series of talks will discuss connections between Riemannian geometry and contact topology. Both structures have deep connections to the topology of 3-manifolds, but there has been little study of the interactions between them (at least the implications in contact topology). We will see that there are interesting connections between curvature and properties of contact structures. The talks will give a brief review of both Riemannian geometry and contact topology and then discuss various was one might try to connect them. There will be many open problems discussed (probably later in the series). 

Numerical Methods for Optimal Transport Problems

Series
Dissertation Defense
Time
Friday, April 12, 2024 - 13:30 for 1.5 hours (actually 80 minutes)
Location
Skiles 268
Speaker
Daniyar OmarovSchool of Mathematics, Georgia Tech

I will present numerical methods for solving the optimal transport (OT) problems in three settings. Firstly, I will discuss discrete OT problems from the perspective of linear programming and assignment problems. Additionally, I will provide a solution for a discrete problem with an obstacle in the domain.

Next, I will consider and compare several different numerical methods to solve the classic continuous OT problem with the squared Euclidean cost function. I will compare two numerical methods used for the fluid dynamics formulation with a direct discretization of the Monge-Ampère PDE. Furthermore, I will introduce a new class of problems called separable, for which very accurate methods can be devised. 

Lastly, I propose a novel implementation of Newton's method for solving semi-discrete OT problems for cost functions that are a positive combination of $p$-norms, $1

From Ehrhard to Generalized Bobkov inequality, and more

Series
Stochastics Seminar
Time
Thursday, April 11, 2024 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Galyna LivshytsGeorgia Tech

We discuss a general scheme that allows to realize certain geometric functional inequalities as statements about convexity of some functionals, and, inspired by the work of Bobkov and Ledoux, we obtain various interesting inequalities as their realizations. For example, we draw a link between Ehrhard’s inequality and an interesting extension of Bobkov’s inequality, and several new and more general inequalities are discussed as well. In this talk we discuss a joint project with Barthe, Cordero-Erausquin and Ivanisvili, and also mention briefly some results from a joint project with Cordero-Erausquin and Rotem.

Minimal surfaces in negatively curved manifolds

Series
School of Mathematics Colloquium
Time
Thursday, April 11, 2024 - 11:00 for
Location
Skiles 005
Speaker
Andre NevesUniversity of Chicago

The asymptotic behavior of closed  geodesic on negatively curved spaces occupies a central place in Riemannian geometry. Minimal surfaces are higher dimensional analogies of geodesics and I will talk about some recent developments regarding the growth rate of minimal surfaces in negatively curved manifolds.

The compactness of multilinear Calderón-Zygmund operators

Series
Analysis Seminar
Time
Wednesday, April 10, 2024 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Anastasios FragkosWashington University St Louis

We prove a wavelet T(1) theorem for compactness of multilinear Calderón -Zygmund (CZ) operators. Our approach characterizes compactness in terms of testing conditions and yields a representation theorem for compact CZ forms in terms of wavelet and paraproduct forms that reflect the compact nature of the operator. This talk is based on joint work with Walton Green and Brett Wick.   

The intertwined derivative Schrödinger system of Calogero--Moser--Sutherland type

Series
Math Physics Seminar
Time
Wednesday, April 10, 2024 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Ruoci SunSchool of Mathematics, Georgia Tech

Please Note: Available via zoom at: https://gatech.zoom.us/j/98258240051

This presentation is dedicated to extending both defocusing and focusing Calogero–Moser–Sutherland derivative nonlinear Schrödinger equations (CMSdNLS), which are introduced in Abanov–Bettelheim–Wiegmann [arXiv:0810.5327], Gérard-Lenzmann [arXiv:2208.04105] and R. Badreddine [arXiv:2303.01087, arXiv:2307.01592], to a system of two matrix-valued variables. This new system is an integrable extension and perturbation of the original CMSdNLS equations. Thanks to the conjugation acting method, I can establish the explicit expression for general solutions on the torus and on the real line in my work [hal-04227081].

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