Séance Séminaire

Séminaire Gaston Darboux

Mapping class groupoids and Thompson's groups

We concoct a uniform treatment of mapping class groups with Thompson’s groups and to generalize them. We give a description of the outer automorphism group of free groups as the isotropy group of a groupoid, akin to the mapping class groupoid of Penner. We also illustrate some arithmetic aspects of these groupoids