Fri, 16 May 2025

12:00 - 13:00
Quillen Room

The derived l-modular unipotent block of p-adic GLn

Rose Berry
(University of East Anglia)
Abstract

Complex representations of p-adic groups are in many ways well-understood. The category has Bernstein's decomposition into blocks, and for many groups each block is known to be equivalent to modules over a Hecke algebra. In particular, the unipotent block of GLn (the block containing the trivial representation) is equivalent to the modules over an extended affine hecke algebra of type A. Over \bar{Fl} the situation is more complicated in the general case: the Bernstein block decomposition can fail (eg for SP8), and there is no longer in general an equivalence with the Hecke algebra. However, some groups, such as GLn and its inner forms, still have a Bernstein decomposition. Furthermore, Vigernas showed that the unipotent block of GLn contains a subcategory that is equivalent to modules over the Schur algebra, a mild extension of the Hecke algebra with much of the same theory, and this subcategory generates the unipotent block under extensions. Building on this work, we show that the derived category of the unipotent block of GLn is triangulated-equivalent to the perfect complexes over a dg-enriched Schur algebra. We prove this by combining general finiteness results about Schur algebras with the well-known structure of the l-modular unipotent blocks of GLn over finite fields.

Wed, 28 May 2025
11:00
L5

A central limit theorem and large deviations principle for the generalised Dean--Kawasaki equation with truncated noise on a bounded domain

Shyam Popat
(Mathematical Institute)
Abstract

We begin with motivation on how the study of SPDEs are relevant when interested in fluctuations of particle systems. 

We then present a law of large numbers, central limit theorem and large deviations principle for the generalised Dean--Kawasaki SPDE with truncated noise. 

Our main contribution is the ability to consider the equation on a general $C^2$-regular, bounded domain with Dirichlet boundary conditions. On the particle level the boundary condition corresponds to absorption and injection of particles at the boundary.

The work is based on discussions with Benjamin Fehrman and can be found at https://arxiv.org/pdf/2504.17094 

 

Data-Adaptive Weight-Ensembling for Multi-task Model Fusion
Tang, A Shen, L Luo, Y Liu, S Hu, H Du, B Tao, D International Journal of Computer Vision 1-17 (25 Apr 2025)
Calibration of local volatility models with stochastic interest rates using optimal transport
Joseph, B Loeper, G Obloj, J Finance and Stochastics volume 30 issue 2 397-439 (23 Feb 2026)
Random-Matrix Theory
Keating, J The Princeton Companion to Applied Mathematics 419-428 (01 Jan 2025)
Global Optimality Characterizations and Algorithms for Minimizing Quartically-Regularized Third-Order Taylor Polynomials
Zhu, W Cartis, C (28 Apr 2025)
The time-dependent reproduction number for epidemics in heterogeneous populations
Bouros, I Thompson, R Gavaghan, D Lambert, B Journal of the Royal Society Interface volume 22 issue 228 (09 Jul 2025)
Thu, 19 Jun 2025

11:00 - 12:00
C5

30 years since the Galois characterisation of ℚₚ — Part II.

Benedikt Stock
(University of Oxford)
Abstract

Building on Leo’s talk last week, I will present the full Galois characterisation of henselianity and introduce some of the ‘explicit’ ingredients he referred to during his presentation. In particular, I will describe a Galois cohomology-inspired criterion for distinguishing between different characteristics. I will then outline the full proof of the Galois characterisation of p-adically closed fields, indicating how each of the ingredients enters the argument.

Thu, 12 Jun 2025

11:00 - 12:00
C5

30 years since the Galois characterisation of ℚₚ — Part I

Leo Gitin
(University of Oxford)
Abstract

The absolute Galois group of ℚₚ determines its field structure: a field K is p-adically closed if and only if its absolute Galois group is isomorphic to that of ℚₚ. This Galois-theoretic characterisation was proved by Koenigsmann in 1995, building on previous work by Arason, Elman, Jacob, Ware, and Pop. Similar results were obtained by Efrat and further developed in his 2006 book.

Our project aims to provide an optimal proof of this characterisation, incorporating improvements and new developments. These include a revised proof strategy; Efrat's construction of valuations via multiplicative stratification; the Galois characterisation of henselianity; systematic use of the standard decomposition; and the function field analogy of Krasner-Kazhdan-Deligne type. Moreover, we replace arguments that use Galois cohomology with elementary ones.

In this talk, I will focus on two key components of the proof: the construction of valuations from rigid elements, and the role of the function field analogy as developed via the non-standard methods of Jahnke-Kartas.

This is joint work with Jochen Koenigsmann and Benedikt Stock.

Subscribe to