Skew-amenability of topological groups

TL;DR

This paper investigates skew-amenability in topological groups, providing characterizations, connections with group actions, and criteria to determine skew-amenability, with applications to groups related to Thompson's group and Monod's group.

Contribution

It introduces new characterizations and criteria for skew-amenability in topological groups, including dynamical conditions and concrete examples involving complex transformation groups.

Findings

Characterization of skew-amenability for isometry and automorphism groups

Connection established between skew-amenability and extensive amenability

Criteria developed for skew-amenability in transformation groups

Abstract

We study skew-amenable topological groups, i.e., those admitting a left-invariant mean on the space of bounded real-valued functions left-uniformly continuous in the sense of Bourbaki. We prove characterizations of skew-amenability for topological groups of isometries and automorphisms, clarify the connection with extensive amenability of group actions, establish a F{\o}lner-type characterization, and discuss closure properties of the class of skew-amenable topological groups. Moreover, we isolate a dynamical sufficient condition for skew-amenability and provide several concrete variations of this criterion in the context of transformation groups. These results are then used to decide skew-amenability for a number of examples of topological groups built from or related to Thompson's group $F$ and Monod's group of piecewise projective homeomorphisms of the real line.