Fri, 22 May 2026
12:00
Quillen Room

The Springer Correspondence via Convolution

Will Osborne
(Mathematical Institute Oxford)
Abstract

The Springer correspondence parameterises the irreducible representations of the Weyl group of a complex semisimple Lie algebra by nilpotent orbits. A key ingredient in the construction is the convolution operation, which appears in various forms throughout geometric representation theory. In this talk, we'll introduce the geometry of the Springer resolution, describe the convolution operation, and illustrate how it gives rise to a geometric construction of Weyl group representations.

Fri, 22 May 2026
12:00
L5

The exceptional holography of the M5-brane

Oscar Varela
(Utah State University)
Abstract

The characterisation of the physics of the M5-brane remains an important open problem in string theory. While the superconformal field theory that resides on a planar M5-brane in flat space is poorly understood, other configurations involving M5-branes wrapped on certain manifolds have well-known superconformal field theory descriptions, including class S field theories. In this talk, I will use new methods based on exceptional generalised geometry to describe the gravity duals of class S field theories, compute a universal sector of their light-operator spectrum, and provide, for the first time, a holographic match of their superconformal index.

Fri, 22 May 2026

11:00 - 12:00
L4

Heterogeneity matters: Mathematical insights into eco-evolutionary dynamics in cancer radiotherapy

Dr Giulia Chiari
((Mathematical Institute University of Oxford))
Abstract

Heterogeneity is a fundamental feature of biological systems. Oncology is one of the fields in which this feature is most evident, as its key players are characterised by mutability, plasticity, and often “uncontrolled” dynamics. Whether heterogeneity arises from spatial structure, environmental variability, or cellular traits, effective therapeutic strategies must explicitly account for it in order to eradicate or control tumours.

From a modern perspective, this requires balancing the hit-hard / keep-it-sensitive trade-off, while also considering not only medical but also broader patient-related side effects of treatments. Contemporary medicine is increasingly exploring ways to exploit the very characteristics that have historically made cancer so dangerous, turning them into potential advantages for therapy.

The multiscale nature of tumour systems, together with the need to predict the combined effects of multiple, non-parallelisable processes, makes the development of optimised mathematical tools particularly compelling. Such tools can address questions that are both scientifically challenging and highly relevant from a clinical and humanitarian perspective.

In this seminar, we will analyse tumour masses from a structured population perspective, focusing on the role of heterogeneity in shaping therapeutic strategies. We will first discuss how heterogeneity in phenotypic composition and nutrient distribution influences the eco-evolutionary dynamics of tumour growth. We will then consider more specifically its impact on radiotherapy.

In particular, we will highlight the advantages of mathematically rigorous modelling in bridging theory and biology. We will also adopt a more exploratory perspective, using these models to illustrate how mathematics can serve as a potential decision-support tool for the selection and optimisation of treatment protocols, within an image- and model-driven framework.

The final part of the seminar will focus on potential future developments, with the aim of fostering an open and collaborative discussion on novel perspectives to improve understanding, prediction, and therapeutic optimisation.

Thu, 21 May 2026
17:00
L3

Grothendieck rings of valued fields and related structures

Floris Vermeulen
(Universitat Munster)
Abstract
The Grothendieck ring of a first order structure was introduced by Krajìček-Scanlon and Denef-Loeser, and is the universal ring classifying definable sets up to definable bijections. Alternatively, one may view this ring as a universal Euler characteristic on definable sets. I will give an introduction to these Grothendieck rings and give several examples. Afterwards I will focus on valued fields, and discuss an Ax-Kochen/Ershov principle for computing the Grothendieck ring in terms of the residue field and value group. Such an approach was introduced by Hrushovski-Kazhdan in the algebraically closed case, and we extend it to more general henselian valued fields. This is based on joint work with Mathias Stout.
Thu, 21 May 2026
16:00
Lecture Room 4

The p-adic approach to the Zilber—Pink conjecture

Netan Dogra
(King's College London)
Abstract

The Zilber—Pink conjecture describes the points on an algebraic variety which have 'special' properties. In this talk, I will discuss some new results which can be proved about this, focusing on the examples of subvarieties of a torus, an abelian variety, or a product of modular curves. The method of proof is a generalisation of the Buium—Coleman proof of the Manin—Mumford conjecture. Parts of this are joint work with Sudip Pandit (KCL) and with Arnab Saha (IIT Gandhinagar).

Thu, 21 May 2026

16:00 - 17:00
L5

Learning to Trade

Dr. Hans Buehler
((Mathematical Institute University of Oxford))
Abstract

The path from classic Black& Scholes quant finance to AI-driven trading and hedging. We review a number of recent results and put them in context of a wider strategy.

Thu, 21 May 2026

14:00 - 15:00
Lecture Room 3

A Computational Framework for Infinite-Dimensional Nonlinear Spectral Problems

Prof Matthew J. Colbrook
(Cambridge University)
Abstract

Professor Colbrook is going to talk about: 'A Computational Framework for Infinite-Dimensional Nonlinear Spectral Problems' 

Nonlinear spectral problems -- where the spectral parameter enters operator families nonlinearly -- arise in many areas of analysis and applications, yet a systematic computational theory in infinite dimensions remains incomplete. In this talk, I present a unified framework based on a solve-then-discretise philosophy (familiar, for example, from Chebfun!), ensuring that truncation preserves convergence. The setting accommodates unbounded operators, including differential operators with spectral-parameter-dependent boundary conditions. 
In the first part, I introduce a provably convergent method for computing spectra and pseudospectra under the minimal assumption of gap-metric continuity of operator graphs -- the weakest natural setting in which the resolvent norm remains continuous. 
In the second part, I develop a contour-based framework for discrete spectra of holomorphic operator families, with a complete analysis of stability, convergence, and randomised sketching based on Gaussian probes. This perspective unifies and extends many existing contour integral methods. Examples throughout highlight practical effectiveness and subtle phenomena unique to infinite dimensions, including the perhaps unexpected sensitivity to probe selection when seeking to avoid spectral pollution.

 

 

Thu, 21 May 2026
13:00
L5

Reading off the worldsheet model for 4d N=4 super Yang-Mills

Sean Seet (University of Edinburgh)
Abstract

It is in general nontrivial to construct a 2d worldsheet model whose correlators evaluate to the amplitudes of a target theory. In this talk I will go through a neat, self contained (and to my knowledge, isolated) example in which the matter content and vertex operators of the dual 2d theory can be straightforwardly read off from the action of a 4d theory. Specifically, we will see that a genus 0 worldsheet model whose correlators compute all the tree amplitudes for pure 4d N=4 super Yang-Mills can be essentially derived from the twistor action in elementary steps. We will then discuss the limitations of this approach. There are no twistorial prerequisites assumed.

Thu, 21 May 2026
12:00
Lecture Room 4, Mathematical Institute

A Runtime-Data-Driven Enhancement Preconditioner for PCG for a Sequence of SPD Linear Systems

Jing-Yuan Wang
(University of Macau)
Abstract

Jing-Yuan Wang is going to talk about: 'A Runtime-Data-Driven Enhancement Preconditioner for PCG for a Sequence of SPD Linear Systems'
 

In this work, we propose a runtime-data-driven enhancement preconditioner for improving the convergence of a preconditioned conjugate gradient method for solving a sequence of symmetric positive definite linear systems of equations. The methodology is designed for the situation where a subset of the systems has been solved and the convergence is considered too slow. In such a situation, data generated from the solved problems (residual vectors, intermediate solution vectors, approximate error vectors) are first analyzed by an unsupervised learning algorithm as a 3-step process: (1) dimension reduction; (2) classification of the slow features; (3) construction of projections to each of the feature subspaces. Based on the results of the analysis, one or more enhancement preconditioners are constructed using projection matrices corresponding to the features extracted from the slow convergence subspaces. The enhancement preconditioners are additively incorporated into the existing preconditioners and are employed to solve other systems in the sequence. The enhancement preconditioner can be further enhanced when necessary by repeating this process. Numerical experiments for time-dependent problems, including parabolic and hyperbolic equations, and stochastic elliptic equations demonstrate that the proposed approach improves the convergence considerably for other systems in the sequence when classical preconditioners are insufficient.

 

 

Thu, 21 May 2026

12:00 - 13:00
L3

Turning noise into signal with soft matter models

Alice Thorneywork
(Department of Chemistry, University of Oxford)
Abstract

For more than a hundred years, scientists have carefully analysed the apparently random fluctuations in Brownian trajectories to learn about soft systems. In a more general sense, however, the information hidden within experimental fluctuations is typically underexploited, due to challenges in unambiguously linking fluctuation signatures to underlying physical mechanisms. In this talk, I will discuss our recent work developing new approaches to interpreting fluctuations in experimental data from a variety of soft systems, and thereby turn ‘noise’ into signal. In particular, I will share some recent results taking a fresh look at fluctuations in equilibrium colloidal monolayers. Here, we have combined experiment, simulation and theory to explore how simply counting colloids can reveal details of self and collective dynamics in interacting systems [1,2,3]. I will then discuss ongoing work to extend this understanding to confined driven systems [4], with the long-term goal of elucidating characteristic fluctuations in our synthetic nanopore experiments [5].


[1] E. K. R. Mackay, B. Sprinkle, S. Marbach, A. L. Thorneywork, Phys. Rev X. (2024)

[2] A. Carter, ALT et al., Soft Matter, 21, 3991, (2025)

[3] E. K. R. Mackay, ALT et al., arXiv:2512.17476, (2025)

[4] S. F. Knowles, E. K. R. Mackay, A. L. Thorneywork, J. Chem. Phys., (2024)

[5] S. F. Knowles, A. L. Thorneywork et al., Phys. Rev. Lett, 127, 137801, (2021)

Thu, 21 May 2026
11:00
C3

First order theories as symmetric simplicial profinite sets

Misha Gavrilovich
Abstract

We reformulate the statement that the theory of the free group is stable in terms of simplicial diagram chasing and profinite sets, without any terminology from logic. This includes three characterisations of stability (via indiscernible sequences, counting types, and definable types), and the notions of a first order theory and a model.

We do so by generalising slightly and allowing the universe of a first order structure/model to be an arbitrary (symmetric) simplicial set: formulas and basic predicates now may denote sets of simplices of an arbitrary (symmetric) simplicial set rather than sets of tuples of elements of a set. In this generalised sense the type space functor of a theory is its universal model classifying its usual models: taking the type of a tuple gives a map from a usual model of a theory to its type space functor. We define a property of simplicial maps weaker then being a fibration, and find it appears in the conditions characterising which maps correspond to models, when the generalised semantics is well-behaved, and which symmetric simplicial profinite sets correspond to first order theories.

Wed, 20 May 2026

16:00 - 17:00
L5

Ends of Diabolical Groups

Andrew Wood
(Mathematical Institute University of Oxford)
Abstract

In 1982, Conway introduced the angel-devil game, which is played on an infinite chess board.  For fixed k, the angel moves at most distance k from its current position on its turn.  The devil then blocks a square permanently.  The devil wins if the angel eventually has no legal moves left.  Berlekamp showed the devil wins against the 1-angel.  Conway asked whether there exists k such that the k-angel has a winning strategy against the devil.  This was resolved independently by Kloster, Máthé, and Bowditch in 2006.  Bowditch proposed playing the game on Cayley graphs of finitely generated groups.  A group for which the devil beats the k-angel for every k is called diabolical.  We will explore the ends of these diabolical groups.

Wed, 20 May 2026
16:00
L6

Moments of moments, Sine beta correlations and stochastic zeta

Theo Assiotis
(University of Edinburgh)
Abstract

 I will talk about recent progress on (a) a conjecture of Fyodorov and Keating on supercritical asymptotics of moments of moments of characteristic polynomials of the circular beta ensemble and (b) on the correlation functions of the sine beta point process. This is joint work with Joseph Najnudel.

Wed, 20 May 2026
16:00
L4

On Virtual Representations of Finite Chevalley Groups in Defining Characteristic

Roman Bezrukavnikov
(MIT)
Abstract

Let G be a finite Chevalley group, i.e., the group of F_q points of a reductive group over F_q. Virtual representations of G in defining characteristic can be constructed in two ways, either by Brauer-Nesbitt reduction of complex representations, or by restricting an algebraic representation. G. Lusztig conjectured the shape of formulas connecting the two procedures; I will discuss a realization of his proposal related to decomposition of the class of diagonal for G/B coming from summands in the push-forward of the structure sheaf under Frobenius. 

Time permitting I will discuss a different, unrelated at present, way to describe such virtual representations linking it to homology of an affine Springer fiber. This found application in the work of Tony Feng and Viet Bao Le Hung on Breuil-Mezard conjectures. 

Based on joint works with Finkelberg, Kazhdan and Morton-Ferguson and with Boixeda Alvarez, McBreen and Yun respectively.

Wed, 20 May 2026
16:00
L4

On Virtual Representations of Finite Chevalley Groups in Defining Characteristic

Roman Bezrukavnikov
(MIT)
Abstract

Let G be a finite Chevalley group, i.e., the group of F_q points of a reductive group over F_q. Virtual representations of G in defining characteristic can be constructed in two ways, either by Brauer-Nesbitt reduction of complex representations, or by restricting an algebraic representation. G. Lusztig conjectured the shape of formulas connecting the two procedures; I will discuss a realization of his proposal related to decomposition of the class of diagonal for G/B coming from summands in the push-forward of the structure sheaf under Frobenius. 

Time permitting I will discuss a different, unrelated at present, way to describe such virtual representations linking it to homology of an affine Springer fiber. This found application in the work of Tony Feng and Viet Bao Le Hung on Breuil-Mezard conjectures. 

Based on joint works with Finkelberg, Kazhdan and Morton-Ferguson and with Boixeda Alvarez, McBreen and Yun respectively.

Wed, 20 May 2026
15:00
L4

Quantitative Orbit Equivalence for $\mathbb{Z}$-odometers

Spyridon Petrakos
(Gothenberg)
Abstract

It is known for a long time, due to a celebrated theorem of Ornstein and Weiss, that (classical/plain) orbit equivalence offers no information about ergodic probability measure preserving actions of amenable groups. On the other hand, conjugacy is too intractable, and effectively hopeless to study in full generality. Quantitative orbit equivalence aims to bridge this gap by adding intermediate layers of rigidity— a strategy that has borne fruit already in the late 1960s but was used as a general framework only semi-recently. In this talk, Spyridon Petrakos will introduce aspects of quantitative orbit equivalence and present a complete picture of it for integer odometers. This is joint work with Petr Naryshkin.

Wed, 20 May 2026
11:00
L4

A short course on Rough Stochastic Differential Equations (RSDEs) and Applications (Lecture 1/3)

Prof. Peter Friz
(TU Berlin)
Abstract
Recent advances at the interface of stochastic analysis, rough path theory, stochastic filtering, stochastic control, and mean-field systems have led to a rapidly developing framework for analyzing stochastic dynamics conditioned on common/observation noise. This mini course  will survey how rough stochastic differential equations, introduced in 2021 by A. Hocquet, K. Lê and the speaker, lead to a unifying perspective across several areas of applied probability. (Additional coauthors include F. Bugini, J. Dause, W. Stannat, H. Zhang and P.Zorin-Kranich).
 



 

Further Information

This mini course will develop in three lectures on the Wednesdays 20/5, 3/6, 10/6 at 11am in L4

Tue, 19 May 2026
16:00
L5

Cartan subalgebras of self-similar graph C*-algebras 

Shanshan Hua
(Münster)
Abstract
Self-similar graph C*-algebras, introduced by Exel and Pardo, generalize graph C*-algebras by encoding self-similar group actions on directed graphs. This class of C*-algebras admits natural groupoid models and is broad, covering Nekrashevych algebras and Katsura algebras (and hence UCT Kirchberg algebras). In joint work (WOA III) with Archey, Duwenig, McCormick, Norton, and Yang, we study Cartan subalgebras in self-similar graph C*-algebras beyond the “locally faithful” setting. 
 
For finite source-free graphs, associated graph C*-algebras have Cartan subalgebras described either via the interior of isotropy of the path groupoid, or combinatorially through the so-called "cycline pairs" encoding the dynamics. We obtain analogous results for a large class of self-similar graph C*-algebras, producing Cartan subalgebras through the understanding of “cycline triples” based on dynamical data.
Tue, 19 May 2026
15:00
L6

A virtual fibering criterion for amalgamated free products

Ashot Minasyan
(University of Southampton)
Abstract

Let G be a group acting on a tree. I will discuss necessary conditions for G to have a finitely generated infinite normal subgroup of infinite index. When the edge stabilisers are virtually cyclic this naturally leads to considering (virtual) fibering of G. I will give an “if and only if” criterion for (virtual) fibering in the special case of amalgamated free products over virtually cyclic subgroups. The talk will be based on joint work with Jon Merladet.

Tue, 19 May 2026
14:00
Online

Diameter of Random Spanning Trees in Random Environment

Rongfeng Sun
(National University of Singapore)
Abstract

We introduce a new spanning tree model which we call Random Spanning Trees in Random Environment (RSTRE), which was introduced independently by A. Kúsz. As the inverse temperature beta varies in the underlying Gibbs measure, it interpolates between the uniform spanning tree and the minimum spanning tree. On the complete graph with n vertices, we show that with high probability, the diameter of the random spanning tree is of order n1/2 when β=o(n/log n), and is of order n1/3 when β > n4/3 log n. We conjecture that the diameter exponent linearly interpolates between these two regimes as the power exponent of beta varies. Based on joint work with L. Makowiec and M. Salvi.


 

Further Information

Part of the Oxford Discrete Maths and Probability Seminar, held via Zoom. Please see the seminar website for details.

Tue, 19 May 2026

14:00 - 15:00
C3

Origins of Instability in Networked Dynamical Systems

Prof. Tim Rogers
(University of Bath)
Abstract

Robustness to perturbation is a key topic in the study of complex systems occurring across a wide variety of applications from epidemiology to biochemistry. In this talk I will examine the eigenspectrum of the Jacobian matrices associated to a general class of networked dynamical systems, which contains information on how perturbations to a stationary state develop over time. I will show that stability is always determined by a spectral outlier, but with pronounced differences to the corresponding eigenvector in different regimes. Depending on model details, instability may originate in nodes of anomalously low or high degrees, or may occur everywhere in the network at once. Our results have potentially useful applications in network monitoring to predict or prevent catastrophic failures.

Tue, 19 May 2026
13:00
L2

TBD

Alex Turzillo
(DAMTP )
Tue, 19 May 2026
12:30
C2

Fluid mechanics and irreversible thermodynamics of lithium-ion battery electrolytes

Aaron Baier-Reinio
(Numerical Analysis)
Abstract
Fluid mechanics and ion transport mechanisms within liquid electrolytes are governed by a mathematically rich system of partial differential equations. I will discuss how these equations capture a wide variety of coupled physical processes, yet maintain consistency with fundamental thermodynamic principles. Numerical simulations will also be presented.
Mon, 18 May 2026
16:30
L5

Algebraic type theory 

Steve Awodey
(Carnegie Mellon University)
Abstract
A representable natural transformation u : U* —> U in the category Psh(C) of presheaves on a small category C is a “natural model" of dependent type theory. The type-forming operations may be described as an algebraic structure on u, representing corresponding operations on the type-families classified by u. For example, the dependent product or “Pi-type” is an algebra structure for the polynomial endofunctor
 
P_u : Psh(C) —> Psh(C) .
 
Similar operations on u represent the other type-formers of unit type, dependent sums, and identity types. The latter are given by a recently determined “path-type” structure, which relates such models to cubical (Quillen) model categories.
Mon, 18 May 2026

16:30 - 17:30
L2

Relative entropy method for equations of fluid dynamics

Agnieszka Świerczewska-Gwiazda
(University of Warsaw)
Abstract

This talk discusses various applications of the relative entropy method in the context of fluid mechanics, focusing on weak-strong uniqueness results and asymptotic limits. Particular attention is given to Euler-type equations involving nonlocal interactions. Furthermore, I will present recent results regarding a novel approach to pressureless Euler equations.

Another application of the relative entropy method to be discussed is the unconditional stability of certain radially symmetric steady states for compressible viscous fluids in domains with inflow/outflow boundary conditions. Specifically, we demonstrate that any solution to the associated evolutionary problem, not necessarily radially symmetric, converges to a unique radially symmetric steady state.

Mon, 18 May 2026
16:00
C3

Theta operators on (p-adic) automorphic forms and applications

Haoran Liang
(King's College London)
Abstract

Theta operators are weight-shifting differential operators on  automorphic forms. They play an important role in studying congruences between Hecke eigenforms and their p-adic variation. For instance, the classical theta operator, which acts on q-expansions of modular forms as q·(d/dq), is used crucially in Edixhoven’s proof of the weight part of Serre’s conjecture, Katz’s construction of p-adic L-functions over CM fields, and Coleman’s classicality theorem.

Recent years have witnessed extensive works on understanding theta operators over general Shimura varieties, from both geometric and representation-theoretic perspectives. In this talk, I will hint at some aspects of this fascinating area of research. If time permits, I will discuss my ongoing work on overconvergent theta operators over Siegel Shimura varieties.

Mon, 18 May 2026

15:30 - 16:30
L3

Rough Stochastic Differential Equations (RSDEs) and Applications

Prof. Peter Friz
(Technical University of Berlin)
Abstract

Recent advances at the interface of stochastic analysis, rough path theory, stochastic filtering, stochastic control, and mean-field systems have led to a rapidly developing framework for analyzing stochastic dynamics conditioned on common/observation noice. This talk will survey how rough stochastic differential equations, introduced in 2021 by A. Hocquet, K. Lê and the speaker, lead to a unifying perspective across several areas of applied probability.

(Additional coauthors include F. Bugini, J. Dause, W. Stannat, H. Zhang and P.Zorin-Kranich.)

Mon, 18 May 2026
15:30
L5

The stable Andrews-Curtis conjecture for thickenable group presentations

Marc Lackenby
((Mathematical Institute University of Oxford))
Abstract

The stable Andrews-Curtis conjecture remains one of the most notorious unsolved problems in group theory. It proposes that every balanced presentation of the trivial group can reduced to the standard presentation (with one generator and one relation) using a sequence of simple moves. In my talk, I will focus on group presentations that are ‘thickenable’, which means that their associated 2-complex embeds in a 3-manifold. For such presentations, the stable Andrews-Curtis conjecture is known to hold. In my talk, I will explain how one can also get an explicit exponential-type upper bound on the number of stable Andrews-Curtis moves that are required. This is in sharp contrast to what is known about non-thickenable presentations.

 

Mon, 18 May 2026
14:15
L2

L^2 and twistor metrics for hyperbolic monopoles

Derek Harland
(Leeds)
Abstract

This talk will present a new approach to the geometry of moduli spaces of hyperbolic monopoles.  It is well-known that the L^2 metric on the moduli space of hyperbolic monopoles, defined using a Coulomb gauge fixing condition, diverges. Recently we have shown that a supersymmetry-inspired gauge-fixing condition cures this divergence, resulting in a pluricomplex geometry that generalises the hyperkaehler geometry of euclidean monopole moduli spaces.  We will compare this with metrics introduced by Nash and Bielawski—Schwachhofer, and present explicit calculations of both metrics for charge 2 monopoles.

Mon, 18 May 2026

14:00 - 15:00
Lecture Room 3

Adjoint-Optimized Neural PDEs and the Regularized Newton Method in the Overparameterized Limit

Dr Konstantin Riedl
((Mathematical Institute University of Oxford))
Abstract

Part 1: In the first part of this talk, we develop a convergence analysis for training neural PDEs in the overparameterized limit. Many engineering and scientific fields have recently become interested in modelling terms in PDEs with neural networks (NNs), which requires solving the inverse problem of learning NN terms from observed data in order to approximate missing or unresolved physics in the PDE model. The resulting neural PDE model, being a function of the NN parameters, can be calibrated to the available ground truth data by optimizing over the PDE using gradient descent, where the gradient is evaluated in a computationally efficient manner by solving an adjoint PDE. We study the convergence of the adjoint gradient descent optimization method for training neural PDE models in the limit where both the number of hidden units and the training time tend to infinity, proving convergence of the trained neural PDE solution to the target data.

Part 2: For the second part, we turn towards developing a convergence analysis of the regularized Newton method for training NNs in the overparameterized limit. As the number of hidden units tends to infinity, the NN training dynamics converge in probability to the solution of a deterministic limit equation involving a „Newton neural tangent kernel“ (NNTK). Explicit rates characterizing this convergence are provided and, in the infinite-width limit, we prove that the NN converges exponentially fast to the target data. We show that this convergence is uniform across the frequency spectrum, addressing the spectral bias inherent in gradient descent. Mathematical challenges that need to be addressed in our analysis include the implicit parameter update of the Newton method with a potentially indefinite Hessian matrix and the fact that the dimension of this linear system of equations tends to infinity as the NN width grows.

Mon, 18 May 2026
13:30
C1

Single generation of C*-algebras

Jakub Curda
((Mathematical Institute University of Oxford))
Abstract

One of the problems posed by Kadison in 1967 asks whether every separably acting von Neumann algebra is generated by a single element. The problem remains open in its full generality but significant progress has been made since. One can of course ask the same question in the C*-algebraic setting where, however, counterexamples are abundant even among commutative C*-algebras. I will give an overview of the history of the problem and then discuss some recent results on single generation of C*-algebras associated to graphs and C*-algebras with Cartan subalgebras.

Fri, 15 May 2026
13:00
L4

Geometry and excluded-volume effects in particle systems

Maria Bruna
(Oxford University)
Abstract

I will discuss stochastic systems of interacting particles with non-overlapping constraints, which give rise to so-called excluded-volume interactions. The aim is to derive effective macroscopic equations governing the evolution of particle densities from the underlying microscopic dynamics. When particles possess nontrivial size or shape, geometric constraints become essential: they complicate the coarse-graining process and strongly influence the emergent behaviour of the system. I will present two representative examples, hard spheres and infinitely thin needles, highlighting how geometry enters the macroscopic description

Fri, 15 May 2026

11:00 - 12:00
L2

Prelims Preparation

Abstract

This session is aimed at first-year undergraduates preparing for Prelims exams. A panel of lecturers and current students will share key advice on exam technique and revision strategies, offering practical tips from their own experience.

Fri, 15 May 2026

11:00 - 12:00
L4

Controlling speed of cell decisions: molecular mechanisms harnessing criticality and transient dynamics

Dr Ruben Perez-Carrasco
(Department of Life Sciences Imperial College London)
Abstract

Cells make decisions across developmental biology, immunology, and synthetic biology. These processes are typically described using systems of ordinary differential equations, where mathematical analysis focuses on steady-state solutions. However, understanding how the timing of cell decisions is controlled requires moving beyond this paradigm. In this talk, I will discuss two complementary molecular mechanisms for controlling dynamical speed. First, I will show how timing can be regulated through critical slowing down, and how combining different bifurcations can generate emergent temporal behaviours even in small gene regulatory networks. Secondly, I will address developmental tempo, where embryos from different species execute remarkably similar genetic programmes at different speeds. I will present a mathematical framework based on orbit invariance that allows us to explore potential molecular mechanisms underlying species-specific differences in developmental timing.

Thu, 14 May 2026
17:00
L3

Is Fp((Q)) NTP2?

Blaise Boissonneau
(HHU Düsseldorf)
Abstract

7 years ago, also in Oxford, Sylvy Anscombe and I asked this question, which is part of the general effort to try and understand the model theory of henselian valued fields through dividing lines. In 2024, Sylvy Anscombe and Franziska Jahnke completely classified NIP henselian valued fields. Their methods can be extended, with the help of works of Chernikov, Kaplan and Simon and of Kuhlmann and Rzepka, to NTP2 henselian valued fields, obtaining the following:

  • if a henselian valued field is NTP2, then it is semitame and its residue field is NTP2;
  • if a henselian valued field is separably algebraically maximal Kaplansky and its residue field is NTP2, then it is NTP2.

This covers a large class of fields, but there is still a gap. Notably, Fp((Q)) is in the middle: it is semitame but not Kaplansky.

To answer this question, we studied so called tame henselian fields with finite residue field, and derived quantifier elimination results, namely, we prove that any formula in the language of valued fields reduces to a formula of the form (∃y f(x,y)=0) ∧ φ(v(x)) ∧ ψ(res(x)), where φ and ψ are formulas in the language of ordered groups and of rings, respectively.

In Fp((Q)) specifically, the valuation ring itself is definable with a diophantine formula (ie of the form ∃y f(x,y)=0), reducing further our quantifier elimination result.

Finally, a large chunk of these formulas are known to be NTP2: when f(x,y) is additive in y, the formula ∃y f(x,y)=z is NTP2 (with respect to x and z). Unfortunately, that does not cover all formulas, so the answer to the titular question is still unknown.

Thu, 14 May 2026

16:00 - 17:00
L5

Lévy-Driven Diffusion for time series

Marie Scheid
(Ecole Polytechnique)
Abstract
Diffusion models for time-series generation are typically trained with Gaussian perturbations, which may underrepresent rare but consequential extremes in financial data. Motivated by the heavy-tailed nature of financial time series, we investigate Lévy-Driven Diffusion for Time Series (TSLD), where Gaussian noise is replaced by Lévy α-stable perturbations in an attempt to better capture tail behavior while preserving temporal dynamics. However, we find that Lévy perturbations introduce substantial instability during training and do not consistently improve generative performance. Beyond distributional fit, we assess financial coherence by comparing generated samples against standard stylized facts, including heavy tails, volatility clustering, and weak linear autocorrelation.
 
More broadly, these results highlight the difficulty of evaluating generative models for financial time series. A model may be theoretically appealing from a distributional perspective while still failing to improve stability, temporal coherence, or downstream usefulness. This motivates the need for carefully designed benchmarks that go beyond visual inspection or marginal distribution matching.
Thu, 14 May 2026
16:00
Lecture Room 4

A structure theorem for sets with doubling 4 + $\delta$

Akshat Mudgal
(University of Warwick )
Abstract

A question of Ben Green asks whether every finite set $A$ of integers with doubling constant $K$ must contain a subset $A'$ of comparable size whose doubling is at most $K + o(1)$ due to some explicit algebraic structure on $A'$. This was previously understood in the regime $K < 4 - o(1)$ by work of Eberhard, Green, and Manners, who showed that one can find such a subset $A'$ with density at least $1/2 + o(1)$ inside a long arithmetic progression. In this talk, I will provide a brief survey of this question as well as mention some new progress towards this. This is joint work with Yifan Jing.

Thu, 14 May 2026

14:00 - 15:00
Lecture Room 3

Numerical analysis of oscillatory solutions of compressible flows

Prof Dr Maria Lukacova
(Johannes Gutenberg University Mainz)
Abstract

Speaker Prof Dr Maria Lukacova will talk about 'Numerical analysis of oscillatory solutions of compressible flows'

 

Oscillatory solutions of compressible flows arise in many practical situations.  An iconic example is the Kelvin-Helmholtz problem, where standard numerical methods yield oscillatory solutions. In such a situation,  standard tools of numerical analysis for partial differential equations are not applicable. 

We will show that structure-preserving numerical methods converge in general to generalised solutions, the so-called dissipative solutions. 
The latter describes the limits of oscillatory sequences. We will concentrate on the inviscid flows, the Euler equations of gas dynamics, and mention also the relevant results obtained for the viscous compressible flows, governed by the Navier-Stokes equations.

We discuss a concept of K-convergence that turns a weak convergence of numerical solutions into the strong convergence of
their empirical means to a dissipative solution. The latter satisfies a weak formulation of the Euler equations modulo the Reynolds turbulent stress.  We will also discuss suitable selection criteria to recover well-posedness of the Euler equations of gas dynamics. Theoretical results will be illustrated by a series of numerical simulations.  

 

 

Thu, 14 May 2026
13:00
L5

Numerical computations of periods and monodromy representations

Eric Pichon-Pharabod
Abstract

The period matrix of a smooth complex projective variety encodes the isomorphism between its singular homology and its algebraic De Rham cohomology. Numerical approximations with high precision of the entries of the period matrix allow to recover some algebraic invariants of the variety, such as the Néron-Severi group in the case of surfaces. In this talk, we will see a method relying on the computation of an effective description of the homology for obtaining such numerical approximations of periods of algebraic varieties, and showcase implementations and applications, in particular to computation of the Picard rank of certain K3 surfaces related to Feynman diagrams.

Thu, 14 May 2026

12:00 - 13:00
C5

Isoperimetric planar tilings with unequal cells

Francesco Nobili
(University of Pisa)
Abstract

In this seminar, we consider an isoperimetric problem for planar tilings with possibly unequal repeating cells. We present general existence and regularity results, and we study the classification of planar isoperimetric double tilings, namely tilings with two repeating cells of minimal perimeter. In this case, we explicitly determine the associated energy profile and provide a complete description of the phase transitions. We also comment on possible extensions and discuss some open problems. This is based on joint work with M. Novaga and E. Paolini.

Thu, 14 May 2026

12:00 - 12:30
Lecture Room 4, Mathematical Institute

Regularization Methods for Hierarchical Programming

Daniel Cortild
((Mathematical Institute University of Oxford))
Abstract

Daniel Cortild is going to talk about: 'Regularization Methods for Hierarchical Programming'

We consider hierarchical variational inequality problems, or more generally, variational inequalities defined over the set of zeros of a monotone operator. This framework includes convex optimization over equilibrium constraints and equilibrium selection problems. In a real Hilbert space setting, we combine a Tikhonov regularization and a proximal penalization to develop a flexible double-loop method for which we prove asymptotic convergence and provide rate statements in terms of gap functions. Our method is flexible, and effectively accommodates a large class of structured operator splitting formulations for which fixed-point encodings are available. 

 

Joint work with Meggie Marschner, and Mathias Staudigl (University of Mannheim)

Thu, 14 May 2026

12:00 - 13:00
L3

The rules and patterns of insect aerial combat

Samuel Fabian
(Department of Biology, Oxford University)
Abstract

Insects use flight as far more than a means of getting from A to B. Flight creates an aeiral theatre for interaction, whether between species or among members of the same species. For example, a male dragonfly must hunt for food, fend off rival males, and pursue evasive females in order to reproduce, tasks that all revolve around chasing fast-moving targets. Despite the remarkable diversity of insect species and their aerial behaviours, common patterns emerge in how they exploit speed and manoeuvrability to achieve these goals. Simple geometric guidance laws can describe these flight trajectories with surprising accuracy, revealing shared strategies that underpin insect aerial combat.

Thu, 14 May 2026
11:00
C3

Tilting perfectoid algebras in continuous logic

Jonas van der Schaaf
(Universitat Munster)
Abstract
In this talk, I will discuss how continuous logic can be used to talk about objects in non-Archimedean geometry. I will discuss perfectoid fields and algebras, tilting, and how to treat these using interpretations in continuous logic. I will then discuss some future directions on geometric applications.
Wed, 13 May 2026

16:00 - 17:00
L6

Flows, triangulations and algorithms on 3-manifolds

Layne Hall
(Dept of Mathematics University of Warwick)
Abstract

Pseudo-Anosov flows are a rich class of dynamical systems on 3-manifolds which are studied for their deep connections to the geometry and topology of the underlying space. A modern tool for studying these flows is to capture them with combinatorial objects called veering triangulations. This correspondence lets us study the flows from a computational perspective. In this talk, I will first give an introduction to pseudo-Anosov flows and how they are captured by these ‘old’ triangulations. I will then give a ‘new’ triangulation which captures these flows in greater generality, giving us many new explicit examples. I will finish by discussing how to algorithmically pass between the old and the new.

Wed, 13 May 2026

11:00 - 13:00
L4

The variational approach for 2D Abelian Higgs measure

Abdulwahab Mohamed
(Max Planck Institute)
Abstract

In this talk, we give a construction of the Abelian Yang--Mills--Higgs measure on the two-dimensional torus via the variational approach initiated by Barashkov--Gubinelli. The construction is carried out through a disintegration of measures: we first construct the conditional Higgs measure given a rough gauge field, and then construct the gauge field marginal. This leads to iterated variational problems, one for the Higgs field and one for the gauge field. At the technical level, the starting point is the construction of the renormalised covariant Laplacian associated to a rough gauge field, together with the study of its resolvent. This allows us to define the covariant Gaussian free field, which serves as the reference Gaussian field for the conditional Higgs measure. Finally, we analyse the ratios of determinants that arise from the change-of-measure formula for Gaussian measures. This is joint work with Nikolay Barashkov, Ajay Chandra, Ilya Chevyrev, and Andreas Koller.
 

Tue, 12 May 2026
16:00
L5

Cartan sub-C*-algebras: existence, variety, and rigidity

Grigoris Kopsacheilis
(KU Leuven)
Abstract
Cartan subalgebras in operator algebras are objects of dynamical nature that have a long history, both in von Neumann algebras and C*-algebras. A II_1 factor can behave in many different ways, from admitting no Cartan subalgebra, to having a unique one, to having unclassifiably many (up to suitable notions of equivalence).
 
Much less is known for C*-algebras; while many C*-algebras have canonical Cartan subalgebras, these are usually far from unique even if one prescribes certain topological features, as has been established by now mainly via applications of classification theory. In this talk, we will discuss some situations showcasing the variety of Cartans that a C*-algebra may exhibit, some relevant open questions, and we shall discuss some examples, namely essential extensions of C(S^1) by the compacts, where a form of rigidity occurs, in the sense that all their Cartan subalgebras with spectrum the one point compactification of the naturals can be described.
 
The talk is based on joint work with Wilhelm Winter, and joint work (in progress) with Philipp Sibbel.
Tue, 12 May 2026
15:30
L4

A generalization of elliptic curves to higher dimensions

Valery Alexeev
(University of Georgia)
Abstract
Of course, there are many generalizations of elliptic curves. The one we consider here is a certain class of n-dimensional Calabi-Yau hypersurfaces in a weighted projective space, naturally associated with the Sylvester sequence $2,3,7,43,...,s_n$. The moduli space of such hypersurfaces is a weighted projective space itself. The case of $n=1$ for the Sylvester numbers 2,3 is the familiar case of elliptic curves in the Weierstrass form, and its compactified moduli space is the weighted projective line $P(4,6)$. 
 
For any n, we prove that the moduli space of pairs $(X,D)$ of such Calabi-Yau hypersurfaces $X$ augmented with a hyperplane $D$ at infinity is a connected component of the KSBA moduli space of stable pairs. A side result is a generalization of the theory of elliptic surfaces to higher dimensions. Based on https://arxiv.org/abs/2511.16562.
Tue, 12 May 2026
15:00
L6

Median metric groups

Pénélope Azuelos
(Dept of Maths University of Bristol)
Abstract
Median spaces form a broad and increasingly important class of metric spaces, encompassing both CAT(0) cube complexes and real trees. Finitely generated groups which admit free transitive (or proper cocompact) actions on discrete median spaces — equivalently, on the 0-skeletons of CAT(0) cube complexes — are reasonably well understood.  In contrast, much less is known about their continuous analogue: groups acting freely and transitively on connected median spaces. I will present some methods for constructing such actions, focusing on actions on real trees and their products, and discuss some of the surprising behaviours that show up. Even when considering real trees, the class of groups acting on such spaces is vastly more diverse than in the discrete setting: while any simplicial tree admits at most one free vertex transitive action, we will see that there are 2^{2^{\aleph_0}} pairwise non-isomorphic groups which admit a free transitive action on the universal real tree with continuum valence.
Tue, 12 May 2026
14:30
C2

Try a Policy Internship and Apply Your Maths from Marine Mammals to Much More

Jun Jewell
(WCMB)
Abstract

If you are curious about using your maths outside academia, want to learn new skills, or just want a change of pace from your PhD, then consider a policy internship. During a three-month UKRI policy internship at the Joint Nature Conservation Committee, I worked on assessing the impact of human-made underwater noise on harbour porpoises. I got to see what it was like to work for a government advisory body, and how scientific modelling is used to inform policy and real-world decision making, all whilst occasionally spotting dolphins from my office window. In this talk, I will describe my project and use it as a starting point to discuss internships more broadly: what you can gain from them, how they differ from academic research, and how to apply.