Seminars and Colloquia by Series

Exponential Rank Bounds for Random Matrices

Series
Stochastics Seminar
Time
Thursday, October 1, 2026 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Achintya Polavarapu – Georgia Tech –

A basic question in random matrix theory is how likely a matrix is to have a large rank. For many classical models, this probability decays extremely quickly, but the strongest results often rely on the entries being identically distributed. In this talk, I will discuss how to obtain the same exponential scale for matrices with fully independent, non-identically distributed entries under only a uniform anti-concentration assumption and explain the main ideas that make this possible.

Smallest Singular Values of Weighted Random Matrices

Series
Analysis Seminar
Time
Wednesday, September 30, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Achintya Raya Polavarapu – Georgia Institute of Technology

How close is a random matrix to being singular? This question measures the stability of random linear systems. Classical models treat every direction equally, but in many settings different directions have different scales or variances. We study what happens when a random matrix is deformed by a fixed invertible matrix. Even a diagonal deformation raises a basic question: is stability controlled by the weakest direction, or by the collective geometry of all directions? I will explain why standard estimates miss this geometry and how random subspaces lead to sharper bounds.

Resolution of the Detection Threshold Conjecture for Sparse Random Geometric Graphs

Series
Probability Working Seminar
Time
Tuesday, September 29, 2026 - 15:30 for 1.5 hours (actually 80 minutes)
Location
Skiles 006
Speaker
Cheng Mao – Georgia Tech –

(second of two talks; the first was on Sep. 22)

A random geometric graph (RGG) is generated by first sampling $n$ latent points independently and uniformly from the unit sphere in $R^d$, and then connecting each pair of points if their inner product exceeds a threshold. We study the sharp detection threshold---the largest dimension at which the RGG can be statistically distinguished from the Erdős--Rényi graph with the same edge density $p$. This threshold is conjectured to be $d \asymp (n h(p))^3$, where $h(p)$ is the binary entropy function. Previous works proved this conjecture for dense graphs with constant $p$ and, up to polylogarithmic factors, very sparse graphs with constant average degrees. In this series of two talks, I will discuss a resolution of this conjecture. This is based on joint work with Hang Du, Nike Sun, Yihong Wu, and Jiaming Xu.

Asymptotic stability of the degree-one vortex in the 2D abelian Yang-Mills-Higgs model under equivariant perturbations

Series
PDE Seminar
Time
Tuesday, September 29, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Jonas Lührmann – University of Cologne –

The abelian Yang-Mills-Higgs model on (1 + 2)-dimensional Minkowski space is a classical relativistic field theory, where a scalar complex field is coupled to an electromagnetic field. It admits topological soliton solutions called vortices. We present a proof of the asymptotic stability of the degree-one vortex under equivariant perturbations in the self-dual case.

Ribbon minimal knots and links

Series
Geometry Topology Seminar
Time
Monday, September 28, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Gary Dunkerley – UGA

It has been observed that the relationship of ribbon concordance induces monotonic behavior across several link invariants. 

Resolving a famous open question of Gordon, Agol unified these observations by showing that ribbon concordance induces a partial order on knots in the 3-sphere.

Agol's argument can be extended to show that ribbon concordance likewise induces a partial order on arbitrary links in the 3-sphere.

Perhaps motivated by the slice-ribbon conjecture, it is natural and interesting to ask which knots and links are minimal with respect to this partial order. 

Leveraging recent developments in link Floer homology, I will share new examples of ribbon minimal knots and links. 

Some of this work is joint with Jaewon Lee and Alessio Di Prisa.

Inference-Time Learning Through Context

Series
Applied and Computational Mathematics Seminar
Time
Monday, September 28, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005 and https://gatech.zoom.us/j/94954654170
Speaker
Zhihui Zhu – Ohio State University –

Large language models exhibit a remarkable ability to learn and adapt from context without updating their parameters. In this talk, I will present our recent work on both understanding how foundation models extract task information from context and designing contexts that enable continual improvement during inference. I will first discuss a geometric analysis on in-context learning, providing new insights into how task representations emerge and evolve across layers. I will then discuss how these insights motivate a broader paradigm of inference-time learning, in which context is actively constructed rather than passively consumed. Building on iterative refinement frameworks such as AlphaEvolve, we view context as an evolving memory that stores hypotheses, intermediate solutions, and feedback. Drawing inspiration from optimization and sequential Monte Carlo, we develop principled approaches for designing and updating context over time. Overall, understanding how models read context and how we can systematically write and evolve context may provide a foundation for the next generation of adaptive AI systems.

Nash discriminants

Series
Algebra Seminar
Time
Monday, September 28, 2026 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Hiro Abo – U of Idaho –

In finite games, a Nash equilibrium occurs when no player can increase their payoff by changing their strategy unless others do. According to J. Nash, such a game always has at least one Nash equilibrium when mixed strategies are allowed. This talk discusses when games have an unexpected number of totally mixed Nash equilibrium points. Such games form varieties called Nash discriminants. The main goal of this talk is to discuss a vector bundle approach to exploring the geometric properties of Nash discriminants. Part of this talk is based on joint work with Irem Portakal and Luca Sodomaco. 

The multipermutohedral Chow ring

Series
Combinatorics Seminar
Time
Friday, September 25, 2026 - 15:15 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Anastasia Nathanson – University of Minnesota –

The multipermutohedral Chow ring was introduced in a series of papers by Clader, Damiolini, Eur, Huang, Li, and Ramadas to study moduli spaces with cyclic symmetry. It generalizes Chow rings of permutohedral varieties and type-B Coxeter arrangements. In this talk, we establish the combinatorial structure of the multipermutohedral Chow ring through an explicit Gröbner basis, yielding a Feichtner-Yuzvinsky-type monomial basis and a formula for the Hilbert series. Using this formula, we refine the palindromicity of the Hilbert series. From a representation-theoretic perspective, we also compute the equivariant Hilbert series under two natural group actions and construct combinatorial maps that establish equivariant unimodality and palindromicity.

Stein method, Malliavin calculus and asymptotic independence

Series
Stochastics Seminar
Time
Thursday, September 24, 2026 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Ciprian Tudor – Université de Lille 1

 

We develop an extension of the Stein-Malliavin calculus which allows to measure the Wasserstein distance between the probability distributions of $ (X, Y)$ and $(Z,Y)$, where $X,Y$ are arbitrary random vectors and $ Z\sim N(0, \sigma ^{2})$ is independent of $Y$. In particular, this method allows to quantify the asymptotic independence between sequences of random variables and vectors. We will discuss some particular applications of this method to various limit theorems.

Working with modern AI tools

Series
School of Mathematics Colloquium
Time
Thursday, September 24, 2026 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Matthew Ballard – University of South Carolina

Working productively with modern AI tools requires looking beyond the products as they are currently packaged, identifying the underlying capabilities that are useful for our own goals, and then building systems to make those capabilities an honest net benefit in practice. The aim is to make the tools suit our interests while preserving what we value in mathematics. I will discuss this perspective through examples centered on research and verification.

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