Please note that the list below only shows forthcoming events, which may not include regular events that have not yet been entered for the forthcoming term. Please see the past events page for a list of all seminar series that the department has on offer.

 

Past events in this series


Mon, 13 May 2024
15:30
L5

Generating RAAGs in 1-relator groups

Ashot Minasyan
(Southampton University)
Abstract
Given a finite simplicial graph $\Gamma$, the right angled Artin group (RAAG) $A(\Gamma)$ is generated by the vertices of $\Gamma$ subject to the relations that two vertices commute if and only if they are adjacent in $\Gamma$. RAAGs play an important role in Geometric Group Theory and in Low Dimensional Topology.
 
Given a group $G$, a finite graph $\Gamma$ and a homomorphism $\phi: A(\Gamma) \to G$ one can ask for conditions ensuring that this homomorphism can be "promoted" to an injective one. In my talk I will discuss such criteria in the case when $G$ is a one-relator group and $\Gamma$ is a forest. In particular, I will sketch an argument showing that it is sufficient for $\phi$ to be injective on the positive sub-monoid of $A(\Gamma)$.
 
The talk will be based on joint work with Motiejus Valiunas (University of Wroclaw, Poland).

 
Mon, 03 Jun 2024
15:30
L5

Geometric semi-norms in homology

Stephane Sabourau
(Université Paris-Est Créteil)
Abstract

The simplicial volume of a simplicial complex is a topological invariant
related to the growth of the fundamental group, which gives rise to a
semi-norm in homology. In this talk, we introduce the volume entropy
semi-norm, which is also related to the growth of the fundamental group
of simplicial complexes and shares functorial properties with the
simplicial volume. Answering a question of Gromov, we prove that the
volume entropy semi-norm is equivalent to the simplicial volume
semi-norm in every dimension. Joint work with I. Babenko.