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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

This paper concerns the study of regular Fourier hypergroups through multipliers of their associated Fourier algebras. We establish hypergroup analogues of well-known characterizations of group amenability, introduce a notion of weak…

Functional Analysis · Mathematics 2016-06-21 Mahmood Alaghmandan , Jason Crann

Let G be a locally compact group, and let U be its unitary representation on a Hilbert space H. Endow the space L(H) of linear bounded operators on H with weak operator topology. We prove that if U is a measurable map from G to L(H) then it…

Functional Analysis · Mathematics 2021-05-27 Yulia Kuznetsova

Given an adaptable separated graph, we construct an associated groupoid and explore its type semigroup. Specifically, we first attach to each adaptable separated graph a corresponding semigroup, which we prove is an $E^*$-unitary inverse…

Operator Algebras · Mathematics 2020-02-03 Pere Ara , Joan Bosa , Enrique Pardo , Aidan Sims

We consider the actions of (semi)groups on a locally compact group by automorphisms. We show the equivalence of distality and pointwise distality for the actions of a certain class of groups. We also show that a compactly generated locally…

Dynamical Systems · Mathematics 2019-03-27 C. R. E. Raja , Riddhi Shah

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

A connected graph is called \emph{geodetic} if there is a unique geodesic between each pair of vertices. In this paper we prove that if a finitely generated group admits a Cayley graph which is geodetic, then the group must be virtually…

Group Theory · Mathematics 2024-12-17 Murray Elder , Giles Gardam , Adam Piggott , Davide Spriano , Kane Townsend

In this work we introduce and study a new notion of amenability for actions of locally compact groups on $C^*$-algebras. Our definition extends the definition of amenability for actions of discrete groups due to Claire…

Operator Algebras · Mathematics 2022-05-04 Alcides Buss , Siegfried Echterhoff , Rufus Willett

We investigate correspondences between extreme amenability and amenability of automorphism groups of Fra\"iss\'e-Hrushovski generic structures that are obtained from smooth classes, and their Ramsey type properties of their smooth classes,…

Logic · Mathematics 2016-10-04 Zaniar Ghadernezhad , Hamed Khalilian , Massoud Pourmahdian

In 1999, Benjamini, Lyons, Peres, and Schramm introduced a notion of weighted-amenability for transitive graphs that is equivalent to the amenability of its automorphism group. For unimodular graphs this notion coincides with classical…

Probability · Mathematics 2025-09-16 Grigory Terlov , Ádám Timár

We outline a simple proof of Hulanicki's theorem, that a locally compact group is amenable if and only if the left regular representation weakly contains all unitary representations. This combines some elements of the literature which have…

Functional Analysis · Mathematics 2016-08-29 Nico Spronk

We prove that, if a discrete group $G$ is not inner amenable, then the unit group of the ring of operators affiliated with the group von Neumann algebra of $G$ is non-amenable with respect to the topology generated by its rank metric. This…

Operator Algebras · Mathematics 2025-03-04 Friedrich Martin Schneider

We describe the global structure of totally disconnected locally compact groups having a linear open compact subgroup. Among the applications, we show that if a non-discrete, compactly generated, topologically simple, totally disconnected…

Group Theory · Mathematics 2019-01-17 Pierre-Emmanuel Caprace , Thierry Stulemeijer

We undertake a systematic study of the approximation properties of the topological and measurable versions of the coarse boundary groupoid associated to a sequence of finite graphs of bounded degree. On the topological side, we prove that…

Group Theory · Mathematics 2021-12-30 Vadim Alekseev , Leonardo Biz

Hrushovski proved the Lie model theorem in full generality with model theoretic methods. The theorem states that for every approximate group there exists a generalized definable locally compact model, which, simplifying, is a…

Logic · Mathematics 2025-12-17 Beatrice Degasperi

In this paper we study unimodular amenable groups. The first part is devoted to results on the existence of uniform families of epsilon-quasi tilings for these groups. In this context, constructions of Ornstein and Weiss are extended by…

Spectral Theory · Mathematics 2013-07-31 Felix Pogorzelski , Fabian Schwarzenberger

It is well-known that a Kleinian group is amenable if and only if it is elementary. We establish an analogous property for equivalence relations and foliations with Gromov hyperbolic leaves: they are amenable if and only if they are…

Functional Analysis · Mathematics 2007-05-23 Vadim A. Kaimanovich

Let $\mathbb{G}$ be a compact quantum group and $A\subseteq B$ an inclusion of $\sigma$-finite $\mathbb{G}$-dynamical von Neumann algebras. We prove that the $\mathbb{G}$-inclusion $A\subseteq B$ is strongly equivariantly amenable if and…

Operator Algebras · Mathematics 2025-04-10 K. De Commer , J. De Ro

It is well-known that a complete Riemannian manifold M which is locally isometric to a symmetric space is covered by a symmetric space. Here we prove that a discrete version of this property (called local to global rigidity) holds for a…

Metric Geometry · Mathematics 2019-11-26 Mikael de la Salle , Romain Tessera

We say that an action of a countable discrete inverse semigroup on a locally compact Hausdorff space is amenable if its groupoid of germs is amenable in the sense of Anantharaman-Delaroche and Renault. We then show that for a given inverse…

Operator Algebras · Mathematics 2015-10-14 Ruy Exel , Charles Starling