Topological dynamics on compacta of big mapping class groups

Orateur:	Yusen Long
Localisation:
Type:	Colloque de Géométrie
Site:	UPEC
Salle:	Salle P1 021
Date de début:	20/09/2024 - 11:15
Date de fin:	20/09/2024 - 12:05

A surface is of infinite type if its fundamental group is not finitely generated. In this presentation, we will be interested in the mapping class group of such a surface and its dynamic of continuous action on compacta. As a closed subgroup of index 2 in the automorphism group of the curve graph, this mapping class group is a non-archimedean Polish group. Using the techniques coming from the model theory, we can show that this group is never extremely amenable.