Seminars and Colloquia by Series

Universality in the small-dispersion limit of the Benjamin-Ono equation

Series
PDE Seminar
Time
Tuesday, October 14, 2025 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 154
Speaker
Peter MillerUniversity of Michigan

This talk concerns the Benjamin-Ono (BO) equation of internal wave theory, and properties of the solution of the Cauchy initial-value problem in the situation that the initial data is fixed but the coefficient of the nonlocal dispersive term in the equation is allowed to tend to zero (i.e., the zero-dispersion limit). It is well-known that existence of a limit requires the weak topology because high-frequency oscillations appear even though they are not present in the initial data.  Physically, this phenomenon corresponds to the generation of a dispersive shock wave. In the setting of the Korteweg-de Vries (KdV) equation, it has been shown that dispersive shock waves exhibit a universal form independent of initial data near the two edges of the dispersive shock wave, and also near the gradient catastrophe point for the inviscid Burgers equation from which the shock wave forms. In this talk, we will present corresponding universality results for the BO equation. These have quite a different character than in the KdV case; while for KdV one has universal wave profiles expressed in terms of solutions of Painlevé-type equations, for BO one instead has expressions in terms of classical Airy functions and Pearcey integrals. These results are proved for general rational initial data using a new approach based on an explicit formula for the solution of the Cauchy problem for BO. This is joint work with Elliot Blackstone and Matthew Mitchell, based on other work with Blackstone, Louise Gassot, and Patrick Gérard.

The h-principle fails for prelegendrians in corank 2 fat distributions

Series
Geometry Topology Seminar
Time
Monday, October 13, 2025 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Eduardo FernándezUGA

It is a classical problem to study whether the h-principle holds for certain classes of maximally non-integrable distributions. The most studied case is that of contact structures, where there is a rich interplay between flexibility and rigidity, exemplified by the overtwisted vs tight dichotomy. For other types of maximally non-integrable distributions, no examples of rigidity are currently known.

In this talk I will discuss rigidity phenomena for fat distributions, which can be viewed as higher corank generalizations of contact structures. These admit natural symplectizations and contactizations. I will introduce a natural class of submanifolds in fat manifolds, called prelegendrians, which admit canonical Legendrian lifts to the contactization. The main result of the talk is that these submanifolds exhibit rigidity: in the “standard corank-2 fat manifold” there exists an infinite family of prelegendrian tori, all of them formally equivalent but pairwise not prelegendrian isotopic. In other words, the h-principle fails for prelegendrians. The talk is based on joint work with Álvaro del Pino and Wei Zhou.
 

Measure theoretic approaches for uncertainty propagation

Series
Applied and Computational Mathematics Seminar
Time
Monday, October 13, 2025 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005 and https://gatech.zoom.us/j/94954654170
Speaker
Li WangUniversity of Minnesota

Uncertainty is ubiquitous: both data and physical models inherently contain uncertainty. Therefore, it is crucial to identify the sources of uncertainty and control its propagation over time. In this talk, I will introduce two approaches to address this uncertainty propagation problem—one for the inverse problem and one for the forward problem. The main idea is to work directly with probability measures, treating the underlying PDE as a pushforward map. In the inverse setting, we will explore various variational formulations, focusing on the characterization of minimizers and their stability. In the forward setting, we aim to propose a new approach to tackle high-dimensional uncertainties.

Celestial Mechanics Problems in Cislunar Space

Series
CDSNS Colloquium
Time
Friday, October 10, 2025 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 311
Speaker
Luke PetersonUT Austin

Please Note: Zoom link: https://gatech.zoom.us/j/91390791493?pwd=QnpaWHNEOHZTVXlZSXFkYTJ0b0Q0UT09

 

Cislunar space—the region between Earth and the Moon—has reemerged as a critical area for space exploration. From a mathematical perspective, this region is governed by multi-body dynamics that give rise to rich structures, including invariant manifolds, resonant orbits, and homoclinic chaos. This talk will introduce classical and modern tools from celestial mechanics to analyze motion in the Earth–Moon system, with an emphasis on restricted 3- and 4-body problems. We will discuss how perturbative methods (normal forms) and invariant manifold theory (parameterization method) reveal the underlying organization of the phase space. Particular attention will be placed on connecting the perturbative regime, where classical methods apply, with the realistic system, which often lies far outside that regime, using computer-assisted techniques. Our ultimate goal is to establish rigorous results for the real solar system while enhancing the engineering capabilities needed to design and fly missions, highlighting how mathematics contributes both to theory and to the practical challenges of contemporary space exploration.

No prior knowledge is needed; the talk will be self-contained and accessible. Undergraduates are encouraged to attend. 

Giant Component of Random Graphs with Given Degrees

Series
Combinatorics Seminar
Time
Friday, October 10, 2025 - 15:15 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Corrine YapGeorgia Institute of Technology

Given a feasible degree sequence D, we consider the uniform distribution over all graphs with degree sequence D. In 1995, Molloy and Reed gave a criterion for determining the existence of a giant (i.e. linear in n) component for degree sequences satisfying certain technical conditions; in 2018, Joos, Perarnau, Rautenbach, and Reed gave a refined result that applies to essentially all feasible D. In this talk, we work in the "supercritical" regime and uncover the precise structure of the giant component when it exists, obtaining bounds on the diameter and mixing time of the random walk on the giant which are tight up to polylogarithmic factors. Our techniques involve a variation of core-kernel reduction and analysis of the switch Markov chain. Joint work with Louigi Addario-Berry and Bruce Reed.

Lectures on Kahler Geometry III

Series
Geometry Topology Working Seminar
Time
Friday, October 10, 2025 - 14:00 for 1.5 hours (actually 80 minutes)
Location
Clough Classroom 325
Speaker
Randy Van WhyGeorgia Tech

Please Note: NOTE the seminar room is different from normal!

This series will tie together algebraic, complex analytic, symplectic, and contact geometries together in one coherent story. This will be done via the study of a series of couplets from different fields of geometry:

Algebraic manifolds:
Affine and quasi-projective varieties (non-compact models)
Projective varieties (compact models)

Complex manifolds:
Stein manifolds
Stein compactifications

Symplectic manifolds:
Liouville/ Weinstein geometry
Compact Kahler manifolds 

Depending on how long it takes to discuss these items, I will also attempt to include discussions on:

• Biran-Giroux decompositions of symplectic manifolds • Boothby-Wang bundles and contact plumbings of these • Milnor's fibration theorem for isolated singularities and connections to open book decompositions and Lefschetz fibrations • Open questions and interesting avenues of research

Most of our discussion will, as a side effect, outline the topological structure behind Type IIA String theory (the "topological A-model") which requires a 6-dimensional Calabi-Yau (Kahler) background.

The reasonable effectiveness of continuous time branching processes in understanding evolving network models

Series
Stochastics Seminar
Time
Thursday, October 9, 2025 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Shankar BhamidiUniversity of North Carolina at Chapel Hill

A wide array of network growth models have been proposed across various domains as test beds to understand questions such as the effect of network change point (when a shock to the network changes the probabilistic rules of its evolution) or the role of attributes in driving the emergence of network structure and subsequent centrality measures in real world systems. 

The goal of this talk will be to describe three specific settings where continuous time branching processes give mathematical insight into asymptotic properties of such models. In the first setting, a natural network change point model can be directly embedded into continuous time thus leading to an understanding of long range dependence of the initial network system on subsequent properties imply the difficulty in understanding and estimating network change point. In the second application, we will describe a notion of resolvability where convergence of a simple macroscopic functional in a model of networks with vertex attributes, coupled with stochastic approximation techniques implies local weak convergence of a standard model of nodal attribute driven network evolution to a limit infinite random structure driven by a multitype continuous time branching process. In the second setting, continuous time branching processes only emerge in the limit. In the final setting we will describe network evolution models with delay where once again such processes arise only in the limit. 

Computer Algebra club/seminar

Series
Other Talks
Time
Thursday, October 9, 2025 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Anton LeykinGeorgia Tech

The first meeting of our club/seminar will feature a brief introduction to the three CAS (computer algebra systems): Macaulay2, OSCAR, and SageMath. All of these are open-source software and are used by research mathematicians for algebraic computation. 

Everyone is welcome to the club! The only requirement is being optimistic about using computer algebra to (potentially) help your research.

The Montesinos trick for double branched covers

Series
Geometry Topology Student Seminar
Time
Wednesday, October 8, 2025 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Alex EldridgeGeorgia Tech

Taking the double branched cover of $S^3$ over a knot $K$ is natural way to associate $K$ with a 3-manifold, and to study the double branched cover, we often want a Dehn surgery description for it. The Montesinos trick gives a systematic way to get such a description. In this talk, we will go over the broad statement of this trick: that a rational tangle replacement on the knot corresponds to Dehn surgery on the double branched cover. This gives particularly nice descriptions for some satellites of $K$ as surgery on $K \mathrel\# K^r$. We will also discuss an application of the trick which characterizes the 2-bridge knots with unknotting number 1.

Random growth models

Series
Research Horizons Seminar
Time
Wednesday, October 8, 2025 - 00:30 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Michael DamronGeorgia Tech

Random and irregular growth is all around us. We see it in the form of cancer growth, bacterial infection, fluid flow through porous rock, and propagating flame fronts. In this talk, I will introduce several different models for random growth and the different shapes that can arise from them. Then I will talk in more detail about one model, first-passage percolation, and some of the main questions that researchers study about it.

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