Seminars and Colloquia by Series

TBA by Julia Lindberg

Series
Algebra Seminar
Time
Monday, April 27, 2026 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Julia Lindberg – Georgia Institute of Technology

TBA

TBA by Mike Perlman

Series
Algebra Seminar
Time
Monday, April 20, 2026 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Mike Perlman – University of Alabama

Please Note: There will be a pre-seminar at 10:55-11:25 in Skiles 005.

TBA

A Finite Livsic Theorem for Anosov Flows with Exponentially Small Errors. (note TIME/DATE)

Series
CDSNS Colloquium
Time
Friday, April 17, 2026 - 15:00 for 1 hour (actually 50 minutes)
Location
TBD
Speaker
Thomas O'hare – Northwestern University –

The classical Livsic theorem says that a H\"older cocycle over a transitive Anosov diffeomorphism/flow is a coboundary if and only if it satisfies the periodic obstruction on all periodic orbits. It is natural to ask whether satisfying the periodic obstruction for all closed orbits of period at most $T$ is enough to conclude that the cocycle is, in some quantitative sense, close to being a coboundary. We show that for transitive Anosov flows, this is indeed enough to find an approximate solution to the cohomological equation with error decaying exponentially in $T$, improving on the polynomial rates obtained first by S. Katok for contact flows in dimension 3, and then later Gouëzel and Lefeuvre in higher dimensions. This is joint work with Jonathan DeWitt, Spencer Durham, and James Marshall Reber.

An Elementary Introduction to the Kontsevich Integral II

Series
Geometry Topology Working Seminar
Time
Friday, April 17, 2026 - 14:00 for 1.5 hours (actually 80 minutes)
Location
Skiles 006
Speaker
Thang Le – Georgia 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.

Convergence of ergodic averages from an observational viewpoint

Series
School of Mathematics Colloquium
Time
Friday, April 17, 2026 - 11:00 for
Location
Skiles 005 and 006
Speaker
Lai-Sang Young – New York University –

The Birkhoff Ergodic Theorem describes typical behaviors and averaged quantities with respect to an invariant measure. In this talk, I will focus on "observable" events, equating observability with positive Lebesgue measure. From this observational viewpoint, "typical" means typical with respect to Lebesgue measure. This leads immediately to issues for attractors, where all invariant measures are singular. I will present highlights of developments in smooth ergodic theory that address these questions. The theory of physical and SRB measures applies to dynamical systems that are deterministic as well as random, in finite and infinite dimensions (where observability has to be interpreted differently). This body of ideas argue in favor of convergence of ergodic averages for typical orbits. But the picture is a little more complicated: In the last part of the talk, I will discuss some recent work that shows that in many natural settings (e.g. reaction networks), it is also typical for ergodic averages 
to fluctuate in perpetuity due to heteroclinic-like behavior.

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