Abstracts

Week of September 7, 2025

September 8, 2025
Geometry, Symmetry and Physics Quasimaps to the Flag Variety and Tilting Modules in Category O 4:30pm -
KT 801

Abstract: A quasimap from a curve to a GIT quotient is a map to the stack quotient that is generically stable. The geometry of Laumon spaces (an open subset of quasimaps from P^1 to the flag variety) is closely related to the representation theory of gl_n. It has been shown that one can construct an action of gl_n on the cohomology of Laumon spaces via geometric correspondences, and this cohomology can be identified with dual Verma modules of gl_n under this action. The full moduli space of quasimaps provides a natural compactification of Laumon spaces. I will explain how to construct an action of gl_n on the equivariant cohomology of these moduli spaces and explore its relation to tilting modules in Category O.

September 9, 2025
Geometry & Topology From Mostow's rigidity to the singularity conjecture 4:30pm -
KT 207

Given a finitely supported probability measure on a Kleinian group, Kaimanovich showed that the Poisson boundary of the associated random walk is the boundary of the hyperbolic space equipped with the hitting measure. It has been conjectured that the hitting measure is singular to conformal measures of the Kleinian group. In this talk, we mainly focus on how Mostow’s rigidity can be generalized to show the expected singularity when the Kleinian group is not convex cocompact, which is my joint work with Andrew Zimmer. We also discuss other applications of this general machinery besides the singularity conjecture.

September 11, 2025
Analysis Available Seminar Slot 4:00pm -
TBD
Quantum Topology and Field Theory Spectral networks for cubic differentials 4:30pm -
KT 801

Abstract:  According to the Gaiotto–Moore–Neitzke algorithm, spectral networks associated to differentials on Riemann surfaces can be used to compute the BPS states of certain supersymmetric quantum field theories. The construction of spectral networks associated with cubic differentials admits a particularly simple description in terms of flat geometry: they appear as graphs of straight trajectories that generate new ones upon intersection under certain conditions. We present the notion of spectral core as a refinement of the classical core concept by Haiden, Katzarkov, and Kontsevich in flat surface theory, and show that it precisely controls the birthing process of spectral networks trajectories. As an application, we describe the spectral networks corresponding to polynomial cubic differentials of degree d=3. Time permitting, we will also discuss the problem of characterizing cubic differentials whose associated spectral networks generated by the algorithm have finite complexity. This work is a collaboration with Omar Kidwai. 

September 12, 2025
Friday Morning Seminar Friday Morning Seminar 10:00am -
KT 801

We have impromptu and (sometimes) scheduled talks, on topics in probability, combinatorics, geometry, and dynamics.

Everyone is welcome!