Wed, 20 May 2026
15:00
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.
Tue, 28 Apr 2026
16:00
16:00
L5
The Public and Community Engagement with Research (PCER) team in Research Services is once again celebrating colleagues doing brilliant public and community engagement work. Building on the success of last term, we’ve reopened nominations and are asking you to nominate people who you think deserve to be recognised.
1 April 2026 marks the 250th birthday of Sophie Germain, who is remembered for major contributions to mathematics, ranging from advances in number theory related to Fermat’s Last Theorem to foundational results in elasticity theory. We will celebrate her life and work through four talks for a general audience.
Wed, 01 Apr 2026
18:00
18:00
The Royal Institution, 21 Albemarle Street, London, W1S 4BS
Oxford Mathematics London Public Lecture: Sophie Germain and prime numbers - James Maynard
James Maynard
Further Information
April 1 is French mathematician Sophie Germain's 250th birthday. Her work focused on prime numbers where her fundamental contribution was to connect Fermat’s Last Theorem with questions on the distribution of those numbers. Fermat’s last Theorem is solved, but questions raised by Sophie remain unsolved and relevant now over 200 years later, with important links to internet cryptography as well as pure mathematics. James Maynard will describe Sophie Germain’s work, its relevance to the modern day, and progress towards resolving the questions she asked.
Oxford Mathematician James Maynard is recognised as one of our leading contemporary mathematicians. In 2022 he won a Fields Medal, the highest honour in mathematics.
Please email @email to register to attend in person.
James' talk forms part of an afternoon celebrating Sophie Germain's life and work, with talks by Oxford Mathematician Lukas Brantner on Sophie's life, Ana Caraiani (Imperial College) on Sophie's favourite problem, and Laura Monk (University of Bristol) on Sophie's work on the theory of elastic surfaces.
To find out more and register for the whole afternoon please click here.
The public lecture will be broadcast on the Oxford Mathematics YouTube Channel on Wednesday 29 April at 5-6 pm and any time after (no need to register for the online version).
The afternoon is kindly sponsored by the International Centre for the Mathematical Sciences (ICMS). The Oxford Mathematics Public Lectures are generously supported by XTX Markets.
Tue, 10 Mar 2026
12:00 -
13:00
C1
Cone types of generalised triangle groups
Ana Isaković
(University of Cambridge CMS)
Abstract
In this talk, I will introduce a class of groups called generalised triangle groups. These groups were originally defined by Stallings, and later studied by Caprace, Conder, Kaluba, and Witzel as candidates for non-residually finite hyperbolic groups. Generalised triangle groups have corresponding CW complexes, which allow us to study the groups using combinatorial and geometric techniques. I will demonstrate this by examining cone types for non-positively curved k-fold triangle groups.
Wed, 11 Mar 2026
16:00 -
17:00
L6
A flat torus theorem for hierarchically hyperbolic spaces
Pénélope Azuelos
(University of Bristol)
Abstract
Various coarse and fine notions of non-positive curvature have proven extremely useful to the study of infinite finitely generated groups. One recurring feature of spaces with these properties is that the behaviour of abelian subgroups of their isometry groups is often highly restricted, via results known as flat torus theorems. One notion of coarse non-positive curvature which has proven to be very useful is hierarchical hyperbolicity. Spaces with this property include Gromov-hyperbolic groups, mapping class groups and compact special groups. I will discuss a new flat torus theorem in this setting and compare it to the classical result for CAT(0) spaces. This talk is based on joint work with Mark Hagen.