Virtual Northern German Group Theory Colloquium 2021
Date: Friday 12th November 2021
We start at 2.30 pm
, the virtual room can be entered from 2 pm on.
If you have questions about the programme, then please contact Rebecca Waldecker
If you have technical questions, then please contact
, will be updated frequently! There are abstracts further below.
Abstract for Nick Gill's talk:
- 2.30 - 3.10 pm:
"On Cherlin's conjecture"
- coffee break
- 3.30 – 3.50 pm:
Finite Simple Groups Acting with Fixity 4 -- Update
- 4 – 4.20 pm:
Automatic continuity for Artin groups
- coffee break
- 5 pm – 5.20 pm:
Calculating the Frattini subgroup of a polycyclic group
- 5.30 – 5.50 pm:
The braided Thompson's group F and R_infty property
In this talk I will discuss a conjecture concerning finite groups that arose in model theory.
This conjecture concerns how finite groups act homogeneously on finite relational structures.
Here you should think of a "relational structure" as being something like a
hypergraph whose edges can be different colours and different lengths,
and you should think of "homogeneity" as being a very strong symmetry condition.
Some deep model theory tells us that such actions can be used to organise
finite permutation groups into natural families in a very strong way.
We will discuss this organising principle, and we will discuss some of the
many interesting group theory questions that it throws up.
The short talks will be given by
Abstract for Paula Hähndel's talk
Finite Simple Groups Acting with Fixity 4 -- Update:
In my talk I will discuss group actions with fixity 4,
in particular the most recent developments towards a full
classification of all finite simple groups that act with fixity 4.
This is part of a project initiated by Kay Magaard,
currently worked on jointly with Barbara Baumeister,
Patrick Salfeld and Rebecca Waldecker.
Abstract for Olga Varghese's talk
Automatic continuity for Artin groups:
The conjecture we address says that any abstract group
homomorphism from a locally compact Hausdorff group into an Artin group
is continuous, i. e. all Artin groups are lcH-slender.
We use the clique-cube complex C_Gamma associated to the Artin group
A_Gamma to reduce the automatic continuity conjecture to
Artin groups where the defining graphs are complete.
Under mild algebraic conditions on small parabolic subgroups of
we show that if all special complete subgroups
A_\Delta of A_Gamma are lcH-slender, then A_Gamma is lcH-slender.
Abstract for Matthias Neumann-Brosig's talk
Calculating the Frattini subgroup of a polycyclic group:
We present a novel, practical method to determine the
Frattini subgroup of a polycyclic group. This method is based on new
theoretical investigations about complements and module strucure of
elementary abelian sections in polycyclic groups.
We have implemented our method in GAP and include a discussion of
Joint work with Bettina Eick.
Abstract for Paula Lins' talk
The braided Thompson's group F and R_infty property:
A group automorphism Phi of Gamma induces the
action g*x= gxPhi(g)^-1 on Gamma.
The orbits of such action are called Reidemeister classes.
One says that Gamma$ satisfies the R_infty property if all its
automorphisms have infinitely many Reidemeister classes.
In this talk, we discuss the property
R_infty of groups and the fact that the braided
Thompson's group F satisfies this property.
This is joint work with Yuri Santos Rego and Altair de Oliveira-Tosti.