Thu, 01 May 2025

17:00 - 18:00
L3

C*-algebras satisfying the UCT form an analytic set

Michał Szachniewicz
(University of Oxford)
Abstract

I will sketch a proof of the statement in the title and outline how it is related to Ehrenfeucht–Fraïssé games on C*-algebras. I will provide the relevant background on C*-algebras (and descriptive set theory) and explain how to construct a standard Borel category X that can play a role of their `moduli'. The theorem from the title is an application of the compactness theorem, for a suitable first-order theory whose models correspond to functors from X. If time permits, I will mention some related problems and connections with conceptual completeness for infinitary logic. This talk is based on several discussions with Ehud Hrushovski, Jennifer Pi, Mira Tartarotti, and Stuart White after a reading group on the paper "Games on AF-algebras" by Ben De Bondt, Andrea Vaccaro, Boban Velickovic and Alessandro Vignati.

Thu, 01 May 2025

11:00 - 12:00
C5

Introduction to Arakelov theory

Michał Szachniewicz
(University of Oxford)
Abstract

I will talk about preliminaries in Arakelov geometry. Also, a historical overview will be provided. This talk will be the basis of a later talk about the theory of globally valued fields.

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Abstract 6241: Predicting treatment outcomes from adaptive therapy: a new mathematical biomarker
Gallagher, K Strobl, M Maini, P Anderson, A Cancer Research volume 85 issue 8_Supplement_1 6241-6241 (21 Apr 2025)
Mie Gluckstad
How about Roger Penrose and his obsessional walks? Or a mathematical joke about an errant dog? Or more from agony uncle Josh Bull as he tells us how to best stir your tea? All three and more feature in our latest short films which you can watch on YouTube. Roger's film and the link to them all are in the full article including Mie Gluckstad (image) on the pros and cons of random walks.

College Lecturer (Career Development) in Non-Physical Applied Mathematics at Pembroke College & Stipendiary Lectureship in Applied Mathematics (3 hours) at Lady Margaret Hall

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Outreach Learning and Development Content Coordinator

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Fri, 02 May 2025
13:00
L5

An algebraic derivation of Morse Complexes for poset-graded chain complexes

Ka Man Yim
(Cardiff University)

Note: we would recommend to join the meeting using the Teams client for best user experience.

Abstract

The Morse-Conley complex is a central object in information compression in topological data analysis, as well as the application of homological algebra to analysing dynamical systems. Given a poset-graded chain complex, its Morse-Conley complex is the optimal chain-homotopic reduction of the initial complex that respects the poset grading.  In this work, we give a purely algebraic derivation of the Morse-Conley complex using homological perturbation theory. Unlike Forman’s discrete Morse theory for cellular complexes, our algebraic formulation does not require the computation of acyclic partial matchings of cells.  We show how this algebraic perspective also yields efficient algorithms for computing the Conley complex.  This talk features joint work with Álvaro Torras Casas and Ulrich Pennig in "Computing Connection Matrices of Conley Complexes via Algebraic Morse Theory" (arXiv:2503.09301). 
 

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