Fri, 31 Jan 2025

12:00 - 13:00
Quillen Room

The tilting equivalence for perfectoid fields

Ken Lee
(University of Oxford)
Abstract

We begin with the Fontaine--Wintenberger isomorphism, which gives an example of an extension of Qp and of Fp((t)) with isomorphic absolute Galois groups. We explain how by trying to lift maps on mod p reductions one encounters Witt vectors. Next, by trying to apply the theory of Witt vectors to the two extensions, we encounter the idea of tilting. Perfectoid fields are then defined more-or-less so that tilting may be reversed. We indicate the proof of the tilting correspondence for perfectoid fields following the Witt vectors approach, classifying the untilts of a given characteristic p perfectoid field along the way. To end, we touch upon the Fargues--Fontaine curve and the geometrization of l-adic local Langlands as motivation for globalizing the tilting correspondence to perfectoid spaces.

Fri, 06 Dec 2024

12:00 - 13:00
Quillen Room

Some Uniserial Specht Modules

Zain Kapadia
(Queen Mary University of London)
Abstract
The Representation Theory of the Symmetric Groups is a classical and rich area of combinatorial representation theory. Key objects of study include Specht modules, the irreducible ordinary representations, which can be reduced modulo p (for p prime). In general, these are no longer irreducible and finding their decomposition numbers and submodule structures are key questions in the area. We give sufficient and necessary conditions for a Specht module in characteristic 2, labelled by a hook partition to be a direct sum of uniserial summands.


 

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