Members & Guests

Dr. Holger Kammeyer

Project leader


Karlsruher Institut für Technologie

E-mail: holger.kammeyer(at)kit.edu
Telephone: +49 721 608-43707
Homepage: https://topology.math.kit.edu/21_375.php

Publications within SPP2026

In this note we refine examples by Aka from arithmetic to S-arithmetic groups to show that the vanishing of the i-th ℓ²-Betti number is not a profinite invariant for all i≥2.

 

Related project(s):
18Analytic L2-invariants of non-positively curved spaces

Given an S-arithmetic group, we ask how much information on the ambient algebraic group, number field of definition, and set of places S is encoded in the commensurability class of the profinite completion. As a first step, we show that the profinite commensurability class of an S-arithmetic group with CSP determines the number field up to arithmetical equivalence and the places in S above unramified primes. We include some applications to profiniteness questions of group invariants.

 

Related project(s):
18Analytic L2-invariants of non-positively curved spaces

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