Seminars and Colloquia by Series

Genera of moduli spaces of quasimaps to quiver varieties

Series
Representation Theory, Moduli, and Physics Seminar
Time
Tuesday, April 14, 2026 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Hunter DinkinsMassachusetts Institute of Technology

Given a space X, one can study various "genera", which give cobordism invariants with interesting properties. In this talk, I will consider the case when X is the moduli space of quasimaps from a smooth projective curve C to a Nakajima quiver variety. I will present a number of results on the (twisted virtual equivariant) Hirzebruch genus and elliptic genus of such spaces. Such invariants are often determined by the case when C is genus zero. When the quiver variety is zero-dimensional, the quasimap moduli spaces generalize the variety parameterizing rank 0 quotients of a fixed vector bundle on C. In these cases, we can prove complete formulas which exhibit an a-postiori independence of the equivariant parameters, a phenomenon sometimes called "rigidity". This is based on work in progress with Reese Lance. 

Real bordered Floer homology

Series
Geometry Topology Seminar
Time
Monday, April 13, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Robert LipshitzUniversity of Oregon

Real Heegaard Floer homology is a new invariant of branched double covers, introduced by Gary Guth and Ciprian Manolescu, and inspired by work of Jiakai Li and others in Seiberg-Witten theory. After sketching their construction, we will describe an extension of the "hat" variant to 3-manifolds with boundary, and the algorithm this gives to compute it when the fixed set is connected. We will end with some open questions.

In-Context Operator Learning on the Space of Probability Measures

Series
Applied and Computational Mathematics Seminar
Time
Monday, April 13, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005 and https://gatech.zoom.us/j/94954654170
Speaker
Dixi WangPurdue University

We introduce in-context operator learning on probability measure spaces for optimal transport (OT). The goal is to learn a single solution operator that maps a pair of distributions to the OT map, using only few-shot samples from each distribution as a prompt and without gradient updates at inference. We parameterize the solution operator and develop scaling-law theory in two regimes. In the nonparametric setting, when tasks concentrate on a low-intrinsic-dimension manifold of source– target pairs, we establish generalization bounds that quantify how in-context accuracy scales with prompt size, intrinsic task dimension, and model capacity. In the parametric setting (e.g., Gaussian families), we give an explicit architecture that recovers the exact OT map in context and provide finite-sample excess-risk bounds. Our numerical experiments on synthetic transports and generative modeling benchmarks validate the framework.

The weight-0 compactly supported Euler characteristic of moduli spaces of marked hyperelliptic curves

Series
Algebra Seminar
Time
Monday, April 13, 2026 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Maddie BrandtVanderbilt University

Please Note: There will be a pre-seminar.

Deligne connects the weight-zero compactly supported cohomology of a complex variety to the combinatorics of its compactifications. In this talk, we use this to study the moduli space of n-marked hyperelliptic curves. We use moduli spaces of G-admissible covers and tropical geometry to give a sum-over-graphs formula for its weight-0 compactly supported Euler characteristic, as a virtual representation of S_n. This is joint work with Melody Chan and Siddarth Kannan.

An Elementary Introduction to the Kontsevich Integral

Series
Geometry Topology Working Seminar
Time
Friday, April 10, 2026 - 14:00 for 1.5 hours (actually 80 minutes)
Location
Skiles 006
Speaker
Thang LeGeorgia Tech

This minicourse provides a friendly, step-by-step introduction to the Kontsevich integral. We begin by demystifying the formula and its construction, showing how it serves as a far-reaching generalization of the classical Gauss linking integral. To establish the invariance of the Kontsevich integral, we explore the holonomy of the Knizhnik–Zamolodchikov (KZ) connection on configuration spaces, utilizing the framework of Chen’s iterated integrals. We will then discuss the universality of the Kontsevich integral for both finite-type (Vassiliev) and quantum invariants, culminating in a concrete combinatorial formula expressed through Drinfeld’s associators. Time permitting, we will conclude by constructing the LMO invariant, demonstrating how it functions as a 3-manifold analog of the Kontsevich integral.

Asymptotics of the Resistance of the Critical Series-Parallel Graph via Parabolic PDE Theory

Series
Math Physics Seminar
Time
Friday, April 10, 2026 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Peter MorfePenn State University

 

Hambly and Jordan (2004) introduced the series-parallel graph, a random hierarchial lattice that is easy to define: Start with the graph consisting of one edge connecting two terminal nodes.  At each subsequent step of the construction, perform independent coin flips for each edge of the graph, and replace the edge by two edges in series if the coin is heads-up or two edges in parallel if tails.  This results in a sequence of random graphs, which can be interpreted as a resistor network.  Hambly and Jordan showed that the logarithm of the resistance grows linearly if the coins are biased to land more often heads-up.  In this talk, I will discuss what happens in the critical case when fair coins are used.  Starting with a new recursive distributional equation (RDE) proposed by Gurel-Gurevich, I develop a framework for analyzing RDE's based on parabolic PDE theory and use this to characterize the asymptotic behavior of the log. resistance.  In the sub- or supercritical case (where the coins are biased), I discuss a tantalizing connection to the Fisher-KPP equation and front propagation.

Minimax D-Optimal designs in generalized linear models: Nonasymptotic theory and efficient algorithms

Series
Stochastics Seminar
Time
Thursday, April 9, 2026 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Jacob AguirreGeorgia Tech

We study robust D-optimal experiment design in generalized linear models, choosing design weights to maximize the worst-case determinant of the Fisher information matrix over a convex parameter uncertainty set. This can be thought of as the natural generalization of D-optimal design in linear regression, and the key challenge is that the information matrix depends on the parameter, so the resulting minimax problem is generally not convex-concave. We show that the desired convexity-concavity, in fact, reduces to a scalar curvature condition on the log-partition function of the exponential family, namely its second derivative h must satisfy the inequality h''h ≥ q(h')² for some q > 1. This insight is connected to the notion of Volumetric Barrier (VB) convexity for self-concordant functions, a result first introduced by Tseng et al (2025) in the context of online quantum state estimation. With self-concordant barriers on the design weights simplex and the parameter uncertainty set, the regularized saddle objective becomes a self-concordant convex-concave (SCCC) function, enabling efficient minimax interior-point methods developed by Nemirovski. We also consider the generalization of the framework, where convexity in the model parameter breaks, but the q-inequality holds up to a deficit proportional to h; in this case, our methods are just as applicable. It turns out that this class includes all canonical GLMs, and we identify logistic regression as the hardest model in the class.

This joint work with Dmitrii Ostrovskii.

The Thurston and Alexander norms of a 3-manifold

Series
Geometry Topology Student Seminar
Time
Wednesday, April 8, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Jake Guynee

In 1986, Thurston introduced a norm on the first cohomology of a 3-manifold $M$ and showed that it can be used to study which cohomology classes are induced by a fibration of $M$ over the circle. In 1998, McMullen introduced a norm on first cohomology that depends only on the Alexander polynomial and showed that it provides a lower bound for the Thurston norm. In this talk, we will introduce the Thurston and Alexander norms and explain why there is an inequality relating the two. To do this, we will define the Alexander polynomial in terms of elementary ideals, and we will use this perspective to understand how topological information is encoded in the exponents of the Alexander polynomial.

Finner-like inequalities in the Heisenberg group

Series
Analysis Seminar
Time
Wednesday, April 8, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Kaiyi HuangUniversity of Wisconsin-Madison

We completely characterize the range of $L^p$-boundedness of certain multilinear Radon-like transforms involving vertical projections in the Heisenberg group. This result is now available on arXiv:2603.17147.

A Tale of the Tree-Independence Number

Series
Graph Theory Seminar
Time
Tuesday, April 7, 2026 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Julien Codsi Princeton University

Treewidth is a graph parameter commonly used to quantify how "close" a graph is to a tree. Although it is a cornerstone of structural graph theory and algorithm design, it is nearly useless for algorithmic purposes in many dense graph classes. In this talk, we discuss the tree-independence number, a more versatile graph parameter that replaces the standard width measure with the stability number. We will present recent results aimed at characterizing the graph classes in which this parameter enables sub-exponential time algorithms for problems that are, in general, NP-hard.

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