Commensurations of the outer automorphism group of a universal Coxeter group
Yassine Guerch
Université Paris-Saclay, Orsay, France
Abstract
This paper studies the rigidity properties of the abstract commensurator of the outer automorphism group of a universal Coxeter group of rank , which is the free product of copies of . We prove that for the natural map is an isomorphism and that every isomorphism between finite index subgroups of is given by a conjugation by an element of .
Cite this article
Yassine Guerch, Commensurations of the outer automorphism group of a universal Coxeter group. Groups Geom. Dyn. 17 (2023), no. 3, pp. 923–983
DOI 10.4171/GGD/718