Tue, 28 Apr 2020
15:30
Virtual

Percolation on triangulations, and a bijective path to Liouville quantum gravity

Olivier Bernardi
(Brandeis)
Further Information

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

Abstract

I will discuss the percolation model on planar triangulations, and present a bijection that is key to relating this model to some fundamental probabilistic objects. I will attempt to achieve several goals:
1. Present the site-percolation model on random planar triangulations.
2. Provide an informal introduction to several probabilistic objects: the Gaussian free field, Schramm-Loewner evolutions, and the Brownian map.
3. Present a bijective encoding of percolated triangulations by certain lattice paths, and explain its role in establishing exact relations between the above-mentioned objects.
This is joint work with Nina Holden, and Xin Sun.

Thu, 07 May 2020
17:00

Around classification for NIP theories

Pierre Simon
(UC Berkeley)
Abstract

I will present a conjectural picture of what a classification theory for NIP could look like, in the spirit of Shelah's classification theory for stable structures. Though most of it is speculative, there are some encouraging initial results about the lower levels of the classification, in particular concerning structures which, in some strong sense, do not contain trees.

Mon, 04 May 2020
15:45
Virtual

Virtually algebraically fibered congruence subgroups

Ian Agol
(UC Berkeley)
Abstract

Addressing a question of Baker and Reid,

we give a criterion to show that an arithmetic group 

has a congruence subgroup that is algebraically

fibered. Some examples to which the criterion applies

include a hyperbolic 4-manifold group containing infinitely

many Bianchi groups, and a complex hyperbolic surface group.

This is joint work with Matthew Stover.

Mon, 01 Jun 2020
15:45
Virtual

Trying to understand mapping class groups of algebraic surfaces from the Thurstonian point of view

Benson Farb
(University of Chicago)
Abstract

In some ways the theory of mapping class groups of 4-manifolds is in 2020 at the same place where the theory of mapping class groups of 2-manifolds was in 1973, before Thurston changed everything.  In this talk I will describe some first steps in an ongoing joint project with Eduard Looijenga where we are trying to understand mapping class groups of certain algebraic surfaces (e.g. rational elliptic surfaces, and also K3 surfaces) from the Thurstonian point of view.

Fri, 12 Jun 2020

16:00 - 17:00
Virtual

North Meets South

Paolo Aceto
Abstract

Paolo Aceto

Knot concordance and homology cobordisms of 3-manifolds 

We introduce the notion of knot concordance for knots in the 3-sphere and discuss some key problems regarding the smooth concordance group. After defining homology cobordisms of 3-manifolds we introduce the integral and rational homology cobordism groups and briefly discuss their relationship with the concordance group. We conclude stating a few recent results and open questions on the structure of these groups.

Fri, 22 May 2020

16:00 - 17:00
Virtual

North Meets South

Lucie Domino and Clemens Koppensteiner
(University of Oxford)
Abstract
Lucie Domino
How to build 3D shapes from flat sheets using a three-centuries old theory
 
In this talk, I’ll present some of our recent work on morphing structures. We start from flat two-dimensional sheets which have been carefully cut and transform them into three-dimensional axisymmetric structures by applying edge-loads. We base our approach on the well-known Elastica theory developed by Euler to create structures with positive, negative, and variable Gaussian curvatures. We illustrate this with famous architectural examples, and verify our theory by both numerical simulations and physical experiments.
 
 
Clemens Koppensteiner
Logarithmic Riemann-Hilbert Correspondences

The classical Riemann-Hilbert correspondence is an elegant statement linking geometry (via flat connections) and topology (via local systems). However, when one allows the connections to have even simple singularities, the naive correspondence breaks down. We will outline some work on understanding this "logarithmic" setting.
Fri, 01 May 2020

16:00 - 17:00
Virtual

Guidance in applying for EPSRC fellowships

Laura McDonnell
(UKRI EPSRC)
Abstract

In this session, Laura will explain the process of applying for an EPSRC fellowship. In particular, there will be a discussion on the Future Leaders Fellowships, New Investigator Awards and Standard Grant applications. There will also be a discussion on applying for EPSRC funding more generally. Laura will answer any questions that people have. 

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