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Extensive amenability is a property of group actions which has recently been used as a tool to prove amenability of groups. We study this property and prove that it is preserved under a very general construction of semidirect products. As…

Group Theory · Mathematics 2021-03-26 Kate Juschenko , Nicolás Matte Bon , Nicolas Monod , Mikael de la Salle

We give a complete characterization of the locally compact groups that are non-elementary Gromov-hyperbolic and amenable. They coincide with the class of mapping tori of discrete or continuous one-parameter groups of compacting…

Group Theory · Mathematics 2015-10-29 Pierre-Emmanuel Caprace , Yves de Cornulier , Nicolas Monod , Romain Tessera

We show the uniqueness of minimal actions of a compact Kac algebra with amenable dual on the AFD factor of type II$_1$. This particularly implies the uniqueness of minimal actions of a compact group. Our main tools are a Rohlin type…

Operator Algebras · Mathematics 2009-11-11 Toshihiko Masuda , Reiji Tomatsu

In the context of (not necessarily minimal) actions, we consider the mean diameter and use it to characterize regular factor maps. Building on this characterization, we prove that an action is diam-mean equicontinuous if and only if it is a…

Dynamical Systems · Mathematics 2025-10-28 Till Hauser

We discuss conditions for unique ergodicity of a collective random walk on a continuous circle. Individual particles in this collective motion perform independent (and different in general) random walks conditioned by the assumption that…

Dynamical Systems · Mathematics 2015-06-18 Michael Blank

We give necessary and sufficient conditions for joint ergodicity results of collections of sequences with respect to systems of commuting measure preserving transformations. Combining these results with a new technique that we call…

Dynamical Systems · Mathematics 2024-12-19 Nikos Frantzikinakis , Borys Kuca

We generalize the notion of isoperimetric profiles of finitely generated groups to their actions by measuring the boundary of finite subgraphings of the orbit graphing. We prove that like the classical isoperimetric profiles for groups,…

Dynamical Systems · Mathematics 2023-10-05 Zihan Xia

We extend some properties of random walks on hyperbolic groups to random walks on convergence groups. In particular we prove that if a convergence group $G$ acts on a compact metrizable space $M$ with the convergence property then we can…

Geometric Topology · Mathematics 2020-06-16 Aitor Azemar

In this paper, we first prove the variational principle for amenable packing topological pressure. Then we obtain an inequality concerning amenable packing pressure for factor maps. Finally, we show that the equality about packing…

Dynamical Systems · Mathematics 2024-05-27 Ziqing Ding , Ercai Chen , Xiaoyao Zhou

We propose a model to represent the motility of social elements. The model is completely deterministic, possesses a small number of parameters, and exhibits a series of properties that are reminiscent of the behavior of comunities in…

Adaptation and Self-Organizing Systems · Physics 2009-11-13 A. Parravano , L. M. Reyes

We show that the group of bounded automatic automorphisms of a rooted tree is amenable, which implies amenability of numerous classes of groups generated by finite automata. The proof is based on reducing the problem to showing amenability…

Group Theory · Mathematics 2019-12-19 Laurent Bartholdi , Vadim A. Kaimanovich , Volodymyr V. Nekrashevych

Let $X$ be a second countable locally compact Abelian group. We prove some group analogues of the Skitovich--Darmois, Heyde and Kac--Bernstein characterisation theorems for $Q$-independent random variables taking values in the group $X$.…

Probability · Mathematics 2018-01-08 Margaryta Myronyuk

We construct some new cohomology theories for topological groups and Lie groups and study some of its basic properties. For example, we introduce a cohomology theory based on measurable cochains which are continuous in a neighbourhood of…

General Topology · Mathematics 2010-09-24 Arati S. Khedekar , C. S. Rajan

We prove a characterization of the amenability of countable Borel equivalence relations in terms of the uniform Liouville property for group actions on their classes. Furthermore, inspired by a well-known amenability criterion for locally…

Group Theory · Mathematics 2026-03-10 Maksym Chaudkhari , Kate Juschenko , Friedrich Martin Schneider

We prove pointwise and maximal ergodic theorems for probability measure preserving (p.m.p.) actions of any countable group, provided it admits an essentially free, weakly mixing amenable action of stable type $III_1$. We show that this…

Dynamical Systems · Mathematics 2011-12-30 Lewis Bowen , Amos Nevo

A recent result of Frantzikinakis establishes sufficient conditions for joint ergodicity in the setting of $\mathbb{Z}$-actions. We generalize this result for actions of second-countable locally compact abelian groups. We obtain two…

Dynamical Systems · Mathematics 2022-06-14 Andrew Best , Andreu Ferré Moragues

Given a topologically free action of a countably infinite amenable group on the Cantor set, we prove that, for every subgroup $G$ of the topological full group containing the alternating group, the group von Neumann algebra $\mathscr{L} G$…

Operator Algebras · Mathematics 2023-11-15 David Kerr , Spyridon Petrakos

We construct approximately inner actions of discrete amenable groups on strongly amenable subfactors of type II_1 with given invariants, and obtain classification results under some conditions. We also study the lifting of the relative \chi…

Operator Algebras · Mathematics 2007-05-23 Toshihiko Masuda

Topological groupoids admit various types of morphisms. We push these notions to the level of continuous groupoid actions to obtain various types of groupoid action morphisms. Some dynamical properties and their relation to these morphisms…

Dynamical Systems · Mathematics 2021-05-04 F. Flores , M. Mantoiu

We study double averages along orbits for measure preserving actions of $\mathbb{A}^\omega$, the direct sum of countably many copies of a finite abelian group $\mathbb{A}$. In this article we show an $L^p$ norm-variation estimate for these…

Dynamical Systems · Mathematics 2019-02-20 Vjekoslav Kovač