Tue, 11 Feb 2025

14:00 - 15:00
L4

Lower bounds for incidences and Heilbronn's triangle problem

Dmitrii Zakharov
(Massachusetts Institute of Technology)
Abstract

Upper bounds on the number of incidences between points and lines, tubes, and other geometric objects, have many applications in combinatorics and analysis. On the other hand, much less is known about lower bounds. We prove a general lower bound for the number of incidences between points and tubes in the plane under a natural spacing condition. In particular, if you take $n$ points in the unit square and draw a line through each point, then there is a non-trivial point-line pair with distance at most $n^{-2/3+o(1)}$. This quickly implies that any $n$ points in the unit square define a triangle of area at most $n^{-7/6+o(1)}$, giving a new upper bound for the Heilbronn's triangle problem.

Joint work with Alex Cohen and Cosmin Pohoata.

Tue, 29 Apr 2025
15:00
L6

Cannon-Thurston maps for the Morse boundary

Matthew Cordes
Abstract

Fundamental to the study of hyperbolic groups is their Gromov boundaries. The classical Cannon--Thurston map for a closed fibered hyperbolic 3-manifolds relates two such boundaries: it gives a continuous surjection from the boundary of the surface group (a circle) to the boundary of the 3-manifold group (a 2-sphere). Mj (Mitra) generalized this to all hyperbolic groups with hyperbolic normal subgroups. A generalization of the Gromov boundary to all finitely generated groups is called the Morse boundary. It collects all the "hyperbolic-like" rays in a group. In this talk we will discuss Cannon--Thurston maps for Morse boundaries. This is joint work with Ruth Charney, Antoine Goldsborough, Alessandro Sisto and Stefanie Zbinden.

Gas-Induced Bulging in Pouch-Cell Batteries: A Mechanical Model
Giudici, A Chapman, J Please, C (2024)

Here's a snippet from the current series of 'Me and My Maths', excellently edited by Evan. Tommy is a visiting student. 

Covering integers by x2 + dy2
Green, B Soundararajan, K Journal of the Institute of Mathematics of Jussieu volume 24 issue 3 847-889 (18 Mar 2025)
Forty years of the Ellis–Baldwin test
Secrest, N von Hausegger, S Rameez, M Mohayaee, R Sarkar, S Nature Reviews Physics (06 Jan 2025)
On a conjecture of Marton
Gowers, T Green, B Manners, F Tao, T Annals of Mathematics volume 201 issue 2 515-549 (12 Mar 2025)
Tue, 27 May 2025
14:00
L6

Differential graded algebras with entire functional calculus

Jon Pridham
(Edinburgh University)
Abstract

(EFC-DGAs) lead to an algebraic approach to derived analytic geometry, pioneered for more general Fermat theories by Carchedi and Roytenberg.
 
They are well-suited to modelling finite-dimensional analytic spaces, and classical theorems in analysis ensure they give a largely equivalent theory to Lurie's more involved approach via pregeometries. DG dagger affinoid spaces provide a well-behaved class of geometric building blocks whose homotopy theory is governed by the underlying EFC-DGAs. 

Time permitting, I might also say a little about non-commutative generalisations.
 

Green Templeton's annual Ceilidh is in our building again this year on the evening of Friday 24th January at 9.30 pm and we have been reserved 30 free tickets which you can access using the following link and access code.

Burns Night Tickets[ Code: GTCMATHS25

Please use your maths email addresses when booking tickets.

Thu, 23 Jan 2025
16:00
Lecture Room 4

Continuity of heights and complete intersections in toric varieties

Michal Szachniewicz
((University of Oxford))
Abstract

I will describe the contents of a joint project with Pablo Destic and Nuno Hultberg. In the paper we confirm a conjecture of Roberto Gualdi regarding a formula for the average height of the intersection of twisted (by roots of unity) hyperplanes in a toric variety. I will introduce the 'GVF analytification' of a variety, which is defined similarly as the Berkovich analytification, but with norms replaced by heights. Moreover, I will discuss some motivations coming from (continuous) model theory and Arakelov geometry.

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