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We prove that if a totally disconnected locally compact group admits a topologically free boundary, then the reduced crossed product of continuous functions on its Furstenberg boundary by the group is simple. We also prove a partial…

Operator Algebras · Mathematics 2025-04-09 Ryoya Arimoto

It is well known that if $G$ is a countable amenable group and $G \curvearrowright (Y, \nu)$ factors onto $G \curvearrowright (X, \mu)$, then the entropy of the first action must be greater than or equal to the entropy of the second action.…

Dynamical Systems · Mathematics 2014-07-07 Brandon Seward

Generalizing Block and Weinberger's characterization of amenability we introduce the notion of uniformly finite homology for a group action on a compact space and use it to give a homological characterization of topological amenability for…

Group Theory · Mathematics 2010-12-14 Jacek Brodzki , Graham A. Niblo , Piotr Nowak , Nick J. Wright

We prove that any ergodic nonatomic probability-preserving action of an irreducible lattice in a semisimple group, at least one factor being connected and higher-rank, is essentially free. This generalizes the result of Stuck and Zimmer…

Dynamical Systems · Mathematics 2016-03-30 Darren Creutz

We introduce a notion of topological entropy for continuous actions of compactly generated topological groups on compact Hausdorff spaces. It is shown that any continuous action of a compactly generated topological group on a compact…

Group Theory · Mathematics 2015-02-16 Friedrich Martin Schneider

We show that the group C*-algebra of any elementary amenable group is quasidiagonal. This is an offspring of recent progress in the classification theory of nuclear C*-algebras.

Operator Algebras · Mathematics 2014-09-24 Narutaka Ozawa , Mikael Rordam , Yasuhiko Sato

In this paper we show that the minimal value of Furstenberg entropy (along all measures, not restricting to stationary ones) for any amenable action is the same as for the action of the group on itself. Using the boundary amenability result…

Group Theory · Mathematics 2024-05-13 Elad Sayag

In this paper we generalize Kingman's sub-additive ergodic theorem to a large class of infinite countable discrete amenable group actions.

Dynamical Systems · Mathematics 2014-12-23 Anthony H. Dooley , Valentyn Ya. Golodets , Guohua Zhang

We consider an action of a countable amenable group on a compact metric space, focusing on the set of generic points with respect to a fixed F{\o}lner sequence. For a given characteristic class, we prove that the set of points that are…

Dynamical Systems · Mathematics 2025-10-31 Sejal Babel , Martha Łącka , Marcel Mroczek

For every infinite (countable discrete) amenable group $G$ and every positive integer $d$ we construct a minimal $G$-action of mean dimension $d/2$ which cannot be embedded in the full $G$-shift on $([0,1]^d)^G$.

Dynamical Systems · Mathematics 2021-01-06 Lei Jin , Kyewon Koh Park , Yixiao Qiao

We say that a countable group $G$ is McDuff if it admits a free ergodic probability measure preserving action such that the crossed product is a McDuff II_1 factor. Similarly, $G$ is said to be stable if it admits such an action with the…

Operator Algebras · Mathematics 2018-09-17 Tobe Deprez , Stefaan Vaes

It is shown that every accessible group which is integrable orbit equivalent to a free group is virtually free. Moreover, we also show that any integrable orbit-equivalence between finitely generated groups extends to their end…

Dynamical Systems · Mathematics 2016-01-05 Lewis Bowen

We motivate and study the class $\mathcal{C}$ of countable groups $G$ such that the conjugacy relation between minimal actions of $G$ on $\mathbb{R}$ by orientation-preserving homeomorphisms is smooth -- that is, admits a Borel transversal.…

Group Theory · Mathematics 2026-05-14 Joaquín Brum , Martín Gilabert Vio , Nicolás Matte Bon

In a previous paper the authors developed an operator-algebraic approach to Lewis Bowen's sofic measure entropy that yields invariants for actions of countable sofic groups by homeomorphisms on a compact metrizable space and by…

Dynamical Systems · Mathematics 2013-07-22 David Kerr , Hanfeng Li

We say that a finite metric space $X$ can be embedded almost isometrically into a class of metric spaces $C$, if for every $\epsilon > 0$ there exists an embedding of $X$ into one of the elements of $C$ with the bi-Lipschitz distortion less…

Metric Geometry · Mathematics 2019-08-15 Vladimir Zolotov

We study stability properties of amenable locally compact quantum groups under the bicrossed product construction. We obtain as our main result an equivalence between amenability of the bicrossed product and amenability of the matched…

Quantum Algebra · Mathematics 2007-05-23 P. Desmedt , J. Quaegebeur , S. Vaes

In this paper we show that the natural action of the symmetric group acting on the product space $\{0, 1 \}^{\mathbb{N}} $ endowed with a symmetric measure is approximately transitive. We also extend the result to a larger class of…

Dynamical Systems · Mathematics 2020-01-22 B. Mitchell Baker , Thierry Giordano , Radu B. Munteanu

P-E. Caprace and N. Monod isolate the class $\mathscr{X}$ of locally compact groups for which relatively amenable closed subgroups are amenable. It is unknown if $\mathscr{X}$ is closed under group extension. In this note, we exhibit a…

Group Theory · Mathematics 2016-03-07 Phillip Wesolek

A classification theorem is obtained for a class of unital simple separable amenable Z-stable C*-algebras which exhausts all possible values of the Elliott invariant for unital stably finite simple separable amenable Z-stable C*-algebras.…

Operator Algebras · Mathematics 2021-05-05 Guihua Gong , Huaxin Lin , Z. Niu

It is proved that a discrete group $G$ is amenable if and only if for every unitary representation of $G$ in an infinite-dimensional Hilbert space $\cal H$ the maximal uniform compactification of the unit sphere $\s_{\cal H}$ has a…

Functional Analysis · Mathematics 2009-10-31 Vladimir Pestov
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