Calendar

Posted January 16, 2026

Algebra and Number Theory Seminar Questions or comments?

Koustav Mondal, Louisiana State University
TBA

Event contact: Gene Kopp

Posted January 22, 2026

Informal Analysis Seminar Questions or comments?

Hari Narayanan, Louisiana State University
Crash Course on Schrödinger Operators (Part 1)

An expository talk in spectral theory.

Posted January 28, 2026

Geometry and Topology Seminar Seminar website

Konrad Wrobel, University of Texas at Austin
Measure equivalence classification of Baumslag-Solitar groups

We complete the classification of Baumslag-Solitar groups up to measure equivalence by showing all Baumslag-Solitar groups with nonunimodular Bass-Serre tree are measure equivalent (i.e., BS(r,s) with r between 1 and s). The proof makes critical use of combinatorial descriptive set theory tools in the measure class preserving setting and passes through the world of measure equivalence of nonunimodular locally compact groups. In particular, as an intermediate step we obtain measure equivalence couplings between all groups of the form Aut(T_{r,s}) for r between 1 and s where T_{r,s} is the directed tree with r incoming edges and s outgoing edges at each vertex. This is joint work with Damien Gaboriau, Antoine Poulin, Anush Tserunyan, and Robin Tucker-Drob.

Posted January 15, 2026

Informal Geometry and Topology Seminar Questions or comments?

Matthew Lemoine, Louisiana State University
TBD

TBD

Posted January 30, 2026

Combinatorics Seminar Questions or comments?

Tung Nguyen, University of Oxford, UK
Polynomial $\chi$-boundedness for excluding $P_5$

We discuss some ideas behind the recent resolution of a 1985 open problem of Gyárfás, that there is a positive integer k for which every graph with no induced five-vertex path has chromatic number at most the kth power of their clique number.

Posted December 29, 2025
Last modified January 31, 2026

Colloquium Questions or comments?

R. Tyrrell Rockafellar, University of Washington
Dual Problems of Optimization

A surprising discovery in the early days of optimization theory was the prevalence of a new kind of duality. Typical problems then of interest, in which a linear function was to be minimized subject to constraints consisting of equations or inequalities imposed on other linear functions, couldn't be solved without simultaneously solving a partnered problem of maximization in the same category. The solutions to the two problems could be viewed moreover as the best strategies for two opponents is a sort of zero-sum game. This theme is now understood much more broadly as a feature of optimization theory that has been important not only in the design of solution algorithms, but also in extending mathematical analysis beyond the traditions of calculus.