# Geometry & Topology

Event Information Subgroups of the outer automorphism group of a free product
12:10 on Monday November 13, 2017
13:00 on Monday November 13, 2017
HU1018, 215 Huron St.
Camille Horbez

Université Paris Sud

I will present a classification result for subgroups of the outer automorphism group of a free product $G=G_1*...*G_k*F_n$, analogous to Ivanov's decomposition theorem for subgroups of the mapping class group of a closed hyperbolic surface of finite type. The main tool in the proof is a description of the Gromov boundary of the free factor graph of a free product, which is a hyperbolic graph on which this outer automorphism group acts. This is joint work with Vincent Guirardel.