Geometric amenability in totally disconnected locally compact groups
Abstract
We give a short geometric proof of a result of Soardi & Woess and Salvatori that a quasitransitive graph is amenable if and only if its automorphism group is amenable and unimodular. We also strengthen one direction of that result by showing that if a compactly generated totally disconnected locally compact group admits a proper Lipschitz action on a bounded-degree amenable graph then that group is amenable and unimodular. We pass via the notion of geometric amenability of a locally compact group, which has previously been studied by the second author and is defined by analogy with amenability, only using right Folner sets instead of left Folner sets. We also introduce a notion of uniform geometric non-amenability of a locally compact group, and relate this notion in various ways to actions of that group on graphs and to its modular homomorphism.
Keywords
Cite
@article{arxiv.2210.02867,
title = {Geometric amenability in totally disconnected locally compact groups},
author = {Romain Tessera and Matthew Tointon},
journal= {arXiv preprint arXiv:2210.02867},
year = {2023}
}
Comments
18 pages. This version of the article has been accepted for publication, after peer review, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s00209-023-03264-z