Jonathan Fruchter (Oxford): Virtual homology and profinite rigidity
Monday, 16.01.2023 16:15 im Raum SRZ 216/17
Abstract: The virtual n-th betti number of a finitely generated group G
is defined as the supremum over dim_Q(H_2(H;Q)), where H runs through
all finite index subgroups of G. We will show that the only examples of
finitely generated and residually free groups, with a finite virtual
second betti number, are the obvious ones: free, surface and free
abelian groups. We will also discuss how virtual (co)homology (with
coefficients in a finite field) can serve as a profinite invariant, and
use this to resolve a specific case of a conjecture of Bridson and Reid
about the profinite rigidity of direct products of free and surface
groups (joint work with Morales).
Angelegt am Tuesday, 10.01.2023 09:44 von Claudia Rüdiger
Geändert am Tuesday, 10.01.2023 09:44 von Claudia Rüdiger
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