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We introduce an equivariant version of the Cuntz semigroup, that takes an action of a compact group into account. The equivariant Cuntz semigroup is naturally a semimodule over the representation semiring of the given group. Moreover, this…

Operator Algebras · Mathematics 2018-01-08 Eusebio Gardella , Luis Santiago

We consider expansive group actions on a compact metric space containing a special fixed point denoted by $0$, and endomorphisms of such systems whose forward trajectories are attracted toward $0$. Such endomorphisms are called…

Dynamical Systems · Mathematics 2019-02-18 Ville Salo , Ilkka Törmä

Given a minimal action $\alpha$ of a countable group on the Cantor set, we show that the alternating full group $\mathsf{A}(\alpha)$ is non-amenable if and only if the topological full group $\mathsf{F}(\alpha)$ is $C^*$-simple. This…

Group Theory · Mathematics 2022-09-13 Eduardo Scarparo

We explore classifiability of crossed products of actions of countable amenable groups on compact, metrizable spaces. It is completely understood when such crossed products are simple, separable, unital, nuclear and satisfy the UCT: these…

Operator Algebras · Mathematics 2024-05-08 Eusebio Gardella , Shirly Geffen , Rafaela Gesing , Grigoris Kopsacheilis , Petr Naryshkin

We give conditions on the subgroups of the circle to be realized as the subgroups of eigenvalues of minimal Cantor systems belonging to a determined strong orbit equivalence class. Actually, the additive group of continuous eigenvalues…

Dynamical Systems · Mathematics 2015-07-29 Maria Isabel Cortez , Fabien Durand , Samuel Petite

Let $\Gamma$ be a finitely generated group and $X$ be a minimal compact $\Gamma$-space. We assume that the $\Gamma$-action is micro-supported, i.e. for every non-empty open subset $U \subseteq X$, there is an element of $\Gamma$ acting…

Group Theory · Mathematics 2021-07-19 Pierre-Emmanuel Caprace , Adrien Le Boudec , Dominik Francoeur

A probability-measure-preserving action of a countable group is called stable if its transformation-groupoid absorbs the ergodic hyperfinite equivalence relation of type II_1 under direct product. We show that for a countable group G and…

Dynamical Systems · Mathematics 2017-05-18 Yoshikata Kida

It is shown that the Ellis semigroup of a $\mathbb Z$-action on a compact totally disconnected space is completely regular if and only if forward proximality coincides with forward asymptoticity and backward proximality coincides with…

Dynamical Systems · Mathematics 2020-11-16 Marcy Barge , Johannes Kellendonk

We study actions of groups by homeomorphisms on $\mathbf{R}$ (or an interval) that are minimal, have solvable germs at $\pm \infty$ and contain a pair of elements of a certain type. We call such actions coherent. We establish that such an…

Group Theory · Mathematics 2018-02-27 Yash Lodha

We prove that a countable group with an effective minimal non-elementary convergence group action is a Powers group. More strongly we prove that it is a strongly Powers group and thus its non-trivial subnormal subgroups are $C^*$-simple.

Operator Algebras · Mathematics 2011-08-12 Yoshifumi Matsuda , Shin-ichi Oguni , Saeko Yamagata

Cohomology for actions of free abelian groups on the Cantor set has (when endowed with an order structure) provided a complete invariance for orbit equivalence. In this paper, we study a particular class of actions of such groups called…

Dynamical Systems · Mathematics 2017-09-26 Thierry Giordano , Ian F. Putnam , Christian F. SKau

In this paper, we consider semigroup actions of discrete countable semigroups on compact spaces by surjective local homeomorphisms. We introduce notions of continuous one-sided orbit equivalence and continuous orbit equivalence for…

Operator Algebras · Mathematics 2021-09-28 Xiangqi Qiang , Chengjun Hou

We introduce the property of having good subgroups for actions of countable discrete groups on compact metrizable spaces, and show that it implies comparison when the acting group is amenable. As a consequence, free actions on…

Dynamical Systems · Mathematics 2025-01-20 Petr Naryshkin , Spyridon Petrakos

We consider a group $G$ acting on a local dendrite $X$ (in particular on a graph). We give a full characterization of minimal sets of $G$ by showing that any minimal set $M$ of $G$ (whenever $X$ is different from a dendrite) is either a…

Dynamical Systems · Mathematics 2019-01-15 Habib Marzougui , Issam Naghmouchi

The aim of this manuscript is to study some local properties of the topological entropy of a free semigroup action. In order to do that we focus on the set of entropy points of a free semigroup action, show that this set carries the full…

Dynamical Systems · Mathematics 2021-12-22 Fagner B. Rodrigues , Thomas Jacobus , Marcus V. Silva

We study equicontinuous actions of semisimple groups and some generalizations. We prove that any such action is universally closed, and in particular proper. We derive various applications, both old and new, including closedness of…

Group Theory · Mathematics 2017-06-16 Uri Bader , Tsachik Gelander

In this paper we present a fixed point property for amenable hypergroups which is analogous to Rickert's fixed point theorem for semigroups. It equates the existence of a left invariant mean on the space of weakly right uniformly continuous…

Functional Analysis · Mathematics 2015-03-09 Benjamin Willson

For an arbitrary countable discrete infinite group $G$, nonsingular rank-one actions are introduced. It is shown that the class of nonsingular rank-one actions coincides with the class of nonsingular $(C,F)$-actions. Given a decreasing…

Dynamical Systems · Mathematics 2024-01-30 Alexandre I. Danilenko , Mykyta I. Vieprik

In this paper, we introduce topologically stable points, $\beta$-persistent points, $\beta$-persistent property, $\beta$-persistent measures and almost $\beta$-persistent measures for first countable Hausdorff group actions of compact…

Dynamical Systems · Mathematics 2021-11-23 Abdul Gaffar Khan , Tarun Das

We study minimality for continuous actions of abelian semigroups on compact Hausdorff spaces with a free interval. First, we give a necessary and sufficient condition for such a space to admit a minimal action of a given abelian semigroup.…

Dynamical Systems · Mathematics 2018-02-15 Matúš Dirbák , Roman Hric , Peter Maličký , Ľubomír Snoha , Vladimír Špitalský