Amenable wreath products with non almost finite actions of mean dimension zero

TL;DR

This paper constructs new examples of minimal, topologically free actions of amenable groups on the Cantor space that have mean dimension zero but are not almost finite, challenging existing conjectures in dynamical systems.

Contribution

It provides the first examples of such actions for amenable wreath products and introduces the concept of allosteric groups within this context.

Findings

Existence of amenable wreath product actions with mean dimension zero that are not almost finite.

These actions have dynamical comparison, indicating a nuanced dynamical behavior.

First examples of allosteric amenable groups with specific dynamical properties.

Abstract

Almost finiteness was introduced in the seminal work of Kerr as an dynamical analogue of Z-stability in the Toms-Winter conjecture. In this article, we provide the first examples of minimal, topologically free actions of amenable groups that have mean dimension zero but are not almost finite. More precisely, we prove that there exists an infinite family of amenable wreath products that admit topologically free, minimal profinite actions on the Cantor space which fail to be almost finite. Furthermore, these actions have dynamical comparison. This intriguing new phenomenon shows that Kerr's dynamical analogue of Toms-Winter conjecture fails for minimal, topologically free actions of amenable groups. The notion of allosteric group holds a significant position in our study. A group is allosteric if it admits a minimal action on a compact space with an invariant ergodic probability measure that is topologically free but not essentially free. We study allostery of wreath products and provide the first examples of allosteric amenable groups.