Fri, 27 May 2016

11:00 - 12:00
C2

The de Rham algebra

Kevin McGerty
(Oxford)
Abstract

This talk will describe the basic properties of the de Rham algebra, which is a generalisation of the de Rham algebra over smooth schemes, which was introduced by L. Illusie in his monograph 'Complexe cotangent et déformations'.

Wed, 25 May 2016

16:00 - 17:00
C1

Simplicial Boundary of CAT(0) Cube Complexes

Kobert Ropholler
(Oxford)
Abstract

The simplicial boundary is another way to study the boundary of CAT(0) cube complexes. I will define this boundary introducing the relevant terminology from CAT(0) cube complexes along the way. There will be many examples and many pictures, hopefully to help understanding but also to improve my (not so great) drawing skills. 

Thu, 26 May 2016

16:00 - 17:00
C5

Cohomogeneity one Ricci solitons

Alejandro Betancourt
(Oxford)
Abstract

Abstract: Ricci solitons are genralizations of Einstein metrics which have become subject of much interest over the last decade. In this talk I will give a basic introduction to these metrics and discuss how to reformulate the Ricci soliton equation as a Hamiltonian system assuming some symmetry conditions. Using this approach we will construct explicit solutions to the soliton equation for manifolds of dimension 5.

Wed, 11 May 2016

16:00 - 17:00
C1

Commutator Subgroup and Quasimorphisms

Nicolaus Heuer
(Oxford)
Abstract

Quasimorphisms (QM) of groups to the reals are well studied and are linked to stable commutator length (scl) via Bavard Duality- Theorem. The notion of QM can be generalized to yield maps  between groups such that each QM from one group pulls back to a QM in the other.

We will give both a short overview of features of scl and investigate these generalized QMs with large scale properties of the commutator group. 

Tue, 31 May 2016

15:45 - 16:45
L4

Non-reductive GIT for graded groups and curve counting

Greg Berczi
(Oxford)
Abstract
I will start with a short report on recent progress in constructing quotients by actions of non-reductive algebraic groups and extending Mumford's geometric invariant theory to a wide class of non-reductive linear algebraic groups which we call graded groups. I will then explain how certain components of the Hilbert scheme of points on smooth varieties can be described as non-reductive quotients and why this description is especially efficient to study the topology of Hilbert schemes. In particular I will explain how equivariant localisation can be used to develop iterated residue formulae for tautological integrals on geometric subsets of Hilbert schemes and I present new formulae counting curves on surfaces (and more generally hypersurfaces in smooth varieties) with given singularity classes. This talk is based on joint works with Frances Kirwan, Thomas Hawes, Brent Doran and Andras Szenes. 
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