Photo of Ramon

Why do some memories last a lifetime while others fade away? A groundbreaking new study sheds light on this mystery by uncovering hidden patterns of brain activity that support long-term memory. Using a framework inspired by thermodynamics, scientists have developed a novel approach to understanding how different brain regions work together to shape cognition. 

Thu, 12 Jun 2025
16:00
Lecture Room 4

The exceptional zero conjecture for GL(3)

Chris Williams
(University of Nottingham)
Abstract

The BSD conjecture predicts that a rational elliptic curve $E$ has infinitely many points if and only if its $L$-function vanishes at $s=1$.

There are $p$-adic versions of similar phenomena. If $E$ is $p$-ordinary, there is, for example, a $p$-adic analytic analogue $L_p(E,s)$ of the $L$-function, and if $E$ has good reduction, then it has infinitely many rational points iff $L_p(E,1) = 0$. However if $E$ has split multiplicative reduction at $p$ - that is, if $E/\mathbf{Q}_p$ admits a Tate uniformisation $\mathbf{C}_p^{\times}/q^{\mathbf{Z}}$ - then $L_p(E,1) = 0$ for trivial reasons, regardless of $L(E,1)$; it has an 'exceptional zero'. Mazur--Tate--Teitelbaum's exceptional zero conjecture, proved by Greenberg--Stevens in '93, states that in this case the first derivative $L_p'(E,1)$ is much more interesting: it satisfies $L_p'(E,1) = \mathrm{log}(q)/\mathrm{ord}(q) \times L(E,1)/(\mathrm{period})$. In particular, it should vanish iff $L(E,1) = 0$ iff $E(\mathbf{Q})$ is infinite; and even better, it has a beautiful and surprising connection to the Tate period $q$, via the 'L-invariant' $\mathrm{log}(q)/\mathrm{ord}(q)$.

In this talk I will discuss exceptional zero phenomena and L-invariants, and a generalisation of the exceptional zero conjecture to automorphic representations of GL(3). This is joint work in progress with Daniel Barrera and Andrew Graham.

Mon, 10 Mar 2025
13:00
L6

Higher-form Symmetries in Linear Gravity

Adam Kmec
Abstract

Recently, work has been done to understand higher-form symmetries in linear gravity. Just like Maxwell theory, which has both electric and magnetic U(1) higher form symmetries, linearised gravity exhibits analogous structure. The authors of
[https://arxiv.org/pdf/2409.00178] investigate electric and magnetic higher form symmetries in linearised gravity, which correspond to shift symmetries of the graviton and the dual graviton respectively. By attempting to gauge the two symmetries, the authors investigate the mixed ’t Hooft anomalies anomaly structure of linearised gravity. Furthermore, if a specific shift symmetry is considered, the corresponding charges are related to Roger Penrose's quasi-local charge construction.

Based on: [https://arxiv.org/pdf/2410.08720][https://arxiv.org/pdf/2409.00178][https://arxiv.org/pdf/2401.17361]

Defending against diverse attacks in federated learning through consensus-based bi-level optimization
García Trillos, N Kumar Akash, A Li, S Riedl, K Zhu, Y Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences volume 383 issue 2298 (05 Jun 2025)
Thu, 13 Mar 2025
16:00
L6

Parametrising complete intersections

Jakub Wiaterek
(University of Oxford)
Abstract

For some values of degrees d=(d_1,...,d_c), we construct a compactification of a Hilbert scheme of complete intersections of type d. We present both a quotient and a direct construction. Then we work towards the construction of a quasiprojective coarse moduli space of smooth complete intersections via Geometric Invariant Theory.

Don Van Vliet, aka Captain Beefheart, was idiosyncratic  to say the least, blending a range of often experiemental musical styles over 13 albums before giving it all up and devoting himself to abstract expressionist painting (see earlier item) which, to be fair, made him far more money.

Beefheart can be very inaccessible, at least on the first 45 hearings. But fear not, this is him at his most accessible.

Thu, 06 Mar 2025
16:00
L6

Geometry and incompleteness of G_2-moduli spaces

Thibault Langlais
(University of Oxford)
Abstract

Riemannian manifolds with holonomy G_2 form an exceptional class of Ricci-flat manifolds occurring only in dimension 7. In the compact setting, their moduli spaces are known to be smooth (unobstructed), finite-dimensional, and to carry a natural Riemannian structure induced by the L^2-metric; but besides this very little is known about the global properties of G_2-moduli spaces. In this talk, I will review the basics of G_2-geometry and present new results concerning the distance theory and the geometry of the moduli spaces.
 

Thu, 22 May 2025
16:00
Lecture Room 4

Mordell–Weil groups of elliptic curves — beyond ranks

Alex Bartel
(University of Glasgow)
Abstract

If $E/\mathbb{Q}$ is an elliptic curve, and $F/\mathbb{Q}$ is a finite Galois extension, then $E(F)$ is not merely a finitely generated abelian group, but also a Galois module. If we fix a finite group $G$, and let $F$ vary over all $G$-extensions, then what can we say about the statistical behaviour of $E(F)$ as a $\mathbb{Z}[G]$-module? In this talk I will report on joint work with Adam Morgan, in which we investigate the simplest non-trivial special case of this very general question. Our work has surprising connections to questions about frequency of failure of the Hasse principle for genus 1 hyperelliptic curves, and to work of Heath-Brown on 2-Selmer group distributions in quadratic twist families.

Mon, 05 May 2025
14:15
L5

The state of the art in the formalisation of geometry

Heather Macbeth
(Imperial College London)
Abstract
The last ten years have seen extensive experimentation with computer formalisation systems such as Lean. It is now clear that these systems can express arbitrarily abstract mathematical definitions, and arbitrarily complicated mathematical proofs.
 
The current situation, then, is that everything is possible in principle -- and comparatively little is possible yet in practice! In this talk I will survey the state of the art in geometry (differential and algebraic). I will outline the current frontier of what has been formalised, and I will try to explain the main obstacles to progress.
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