Tue, 11 Nov 2025
15:30
L4

How to make log structures

Alessio Corti
(Imperial College London)
Abstract

I will speak about my work with Helge Ruddat on how to construct explicitly log structures and morphisms. I will also discuss some motivation. I will try to stay informal and assume no prior knowledge of log structures.

Deriving Optimal Treatment Timing for Adaptive Therapy: Matching the Model to the Tumor Dynamics
Gallagher, K Strobl, M Anderson, A Maini, P Bulletin of Mathematical Biology volume 87 issue 10 146 (08 Oct 2025)
Hippocampal ripple diversity organizes neuronal reactivation dynamics in the offline brain
Castelli, M Lopes Dos Santos, V Gava, G Lambiotte, R Dupret, D Neuron (02 Oct 2025)
Motivic action for Siegel modular forms
Horawa, A Prasanna, K Journal of the European Mathematical Society

Sometimes artists become better known for their lifestyle or fashion tastes than the work without which we wouldn't know or care about them - Van Gogh, Bowie, even Taylor Swift. Jim Morrison of the Doors fits that bill, in his case for his death and grave as much as his life. But he and the band wrote some songs. That's where it all starts and ends.

Tue, 25 Nov 2025
15:30
L4

Equivariant deformation theory & arithmetic deformations of homogeneous varieties

Noé Sotto
(Université Paris-Saclay, Orsay)
Abstract

Modern approaches to infinitesimal deformations of algebro-geometric objects (like varieties) use the setting of formal moduli problems, from derived geometry. It allows to prove that all kinds of deformations are governed by a tangent complex equipped with a derived Lie algebra structure. I will use this framework to study equivariant deformations of varieties with respect to the action of an algebraic group. Then, I will explain how this theory of equivariant deformations allows us to prove a dichotomous behaviour for almost all varieties that are homogeneous under a reductive group : either they deform to characteristic 0, or they admit no deformation to any ring of characteristic greater than p.

Viscoelastic time responses of polymeric cell substrates measured continuously from 0.1–5000 Hz in liquid by photothermal AFM nanorheology
Adam, C Piacenti, A Zhang, Y Waters, S Contera, S Nanoscale (30 Jul 2025)
Tue, 14 Oct 2025
15:30
L4

Vafa-Witten invariants from modular anomaly

Sergey Alexandrov
(Montpelier)
Abstract
I'll present a modular anomaly equation satisfied by generating functions of refined Vafa-Witten invariants 
for the gauge group $U(N)$ on complex surfaces with $b_1=0$ and $b_2^+=1$, 
which has been derived from S-duality of string theory.
I'll show how this equation can used to find explicit expressions for these generating functions
(and their modular completions) on $\mathbb{CP}^2$, Hirzebruch and del Pezzo surfaces.
The construction for $\mathbb{CP}^2$ suggests also a new form of blow-up identities.
Schur multipliers of C⁎-algebras, group-invariant compactification and applications to amenability and percolation
Mukherjee, C Recke, K Journal of Functional Analysis volume 287 issue 2 110468-110468 (01 Jul 2024)
Photo of Harry

I work in the field of geometric group theory. This is a pretty broad heading, but for me it means that the goal is to understand infinite groups, and the strategy is to get them to act on nice metric spaces that we know a lot about. 

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