On abstract commensurators of groups
نویسنده
چکیده
We prove that the abstract commensurator of a nontrivial free group, an infinite surface group, or more generally a group that splits appropriately over a cyclic subgroup is not finitely generated. This applies in particular to all torsion-free word-hyperbolic groups with infinite outer automorphism group and abelianization of rank at least 2. We also construct a finitely generated group which can be mapped onto Z and which has a finitely generated commensurator.
منابع مشابه
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تاریخ انتشار 2008