Mon, 20 Oct 2025
15:30
L5

Skein modules are holonomic 

David Jordan
(University of Edinburgh)
Abstract
Abstract:  Skein modules capture vector spaces of line operators in 3D Chern-Simons, equivalently line operators constrained to a 3-dimensional boundary in the Kapustin-Witten twist of 4D N=4 gauge theory.  They have an elementary mathemical definition via representation theory of quantum groups.
 
In recent work with Iordanis Romaidis we proved that when the quantum parameter is generic, the skein module of a 3-manifold is finitely generated relative to the skein algebra of its boundary and that moreover the resulting singular support variety is Lagrangian, hence that skein modules are holonomic. Our results confirm and strengthen a conjecture of Detcherry, and imply a conjecture of Frohman, Gelca and LoFaro from 2002 (the latter independently established this year by Beletti and Detcherry using other methods).
 
In the talk I will give an outline of the key ingredients of the proof, which recreate elements of the classical theory of differential operators in the skein setting. 

 
Mon, 13 Oct 2025
15:30
L5

Virtual fibring and Poincaré duality

Dawid Kielak
(Mathematical Institute Oxford)
Abstract

I will talk about the problem of recognising when a manifold admits a finite cover that fibres over the circle, with emphasis on the case of hyperbolic manifolds in odd dimensions. I will survey the state-of-art, and discuss the role that group theory plays in the problem. Finally, I will discuss a recent result that sheds light on the analogous group-theoretic problem, that is, virtual algebraic fibring of Poincaré-duality groups. The final theorem is joint with Sam Fisher and Giovanni Italiano.

Mon, 13 Oct 2025
16:45
L5

Varieties over free associative algebras

Zlil Sela
Abstract
In the 1960s and 1970s ring theorists (P. M. Cohn, G.Bergman and others) tried to study the structure of sets of solutions to systems of (polynomial) equations (varieties) over free associative algebras. They found significant pathologies that demonstrated the difficulty to achieve their goal.
 
In an ongoing joint work with A. Atkarskaya we modify techniques that were used to study varieties over free groups and semigroups to study the structure of varieties over associative algebras. Along the way we find new structures also in free groups and semigroups. 
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