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We prove that if two topologically free and entropy regular actions of countable sofic groups on compact metrizable spaces are continuously orbit equivalent, and each group either (i) contains a w-normal amenable subgroup which is neither…

Dynamical Systems · Mathematics 2022-02-23 David Kerr , Hanfeng Li

Given a minimal action $G\curvearrowright X$ of a countable group $G$ on a compact space $X$, we prove that if the reduced crossed product $G\ltimes_rC(X)$ is simple, then there exists a point whose stabilizer subgroup has trivial amenable…

Operator Algebras · Mathematics 2026-05-22 Yair Hartman , Mehrdad Kalantar

We note a characterization of the amenability of unitary representations (in the sense of Bekka) via the existence of an orthonormal basis supporting an invariant probability charge. Based on this, we explore several natural notions of…

Group Theory · Mathematics 2026-01-06 Paula Kahl , Friedrich Martin Schneider

We completely characterize connected Lie groups all of whose countable subgroups are weakly amenable. We also provide a characterization of connected semisimple Lie groups that are weakly amenable. Finally, we show that a connected Lie…

Functional Analysis · Mathematics 2018-10-17 Søren Knudby

We investigate structural properties of non-sofic groups, assuming that such groups exist. We introduce and study two classes: minimal non-sofic groups and $\omega$-non-sofic groups. For minimal non-sofic groups, we establish strong…

Group Theory · Mathematics 2026-05-18 Kıvanç Ersoy

The concept of a C-approximable group, for a class of finite groups C, is a common generalization of the concepts of a sofic, weakly sofic, and linear sofic group. Glebsky raised the question whether all groups are approximable by finite…

Group Theory · Mathematics 2017-05-25 Nikolay Nikolov , Jakob Schneider , Andreas Thom

We establish new results on the weak containment of quasi-regular and Koopman representations of a second countable locally compact group $G$ associated with non-singular $G$-spaces. We deduce that any two boundary representations of a…

Group Theory · Mathematics 2022-02-15 Pierre-Emmanuel Caprace , Mehrdad Kalantar , Nicolas Monod

This paper demonstrates the uniformly finite homology developed by Block and Weinberger and its relationship to amenable spaces via applications to the Cayley graph of Thompson's Group F. In particular, a certain class of subgraph of F is…

Group Theory · Mathematics 2009-03-11 Dan Staley

We obtain a criterion for quasiconvexity of a subgroup of an amalgamated free product of two word hyperbolic groups along a virtually cyclic subgroup. The result provides a method of constructing new word hyperbolic group in class (Q), that…

Group Theory · Mathematics 2008-02-03 Ilya Kapovich

We give a short geometric proof of a result of Soardi & Woess and Salvatori that a quasitransitive graph is amenable if and only if its automorphism group is amenable and unimodular. We also strengthen one direction of that result by…

Group Theory · Mathematics 2023-06-16 Romain Tessera , Matthew Tointon

We say that a finitely generated group $\Gamma$ is self-simulable if every effectively closed action of $\Gamma$ on a closed subset of $\{\texttt{0},\texttt{1}\}^{\mathbb{N}}$ is the topological factor of a $\Gamma$-subshift of finite type.…

Group Theory · Mathematics 2025-02-25 Sebastián Barbieri , Mathieu Sablik , Ville Salo

For discrete measured groupoids preserving a probability measure we introduce a notion of sofic dimension that measures the asymptotic growth of the number of sofic approximations on larger and larger finite sets. In the case of groups we…

Dynamical Systems · Mathematics 2012-11-13 Ken Dykema , David Kerr , Mikael Pichot

We generalize a result of Hochman in two simultaneous directions: Instead of realizing an effectively closed $\mathbb{Z}^d$ action as a factor of a subaction of a $\mathbb{Z}^{d+2}$-SFT we realize an action of a finitely generated group…

Dynamical Systems · Mathematics 2019-04-26 Sebastián Barbieri , Mathieu Sablik

A group is self-simulable if all its computable actions admit SFT covers, which means roughly that they can be implemented with finitely many tiling constraints. We prove that a graph product of infinite finitely-generated groups is…

Group Theory · Mathematics 2026-05-27 Kanéda Blot , Ville Salo

We show that on an arbitrary finitely generated non virtually solvable linear group, any two independent random walks will eventually generate a free subgroup. In fact, this will hold for an exponential number of independent random walks.

Group Theory · Mathematics 2019-12-19 Richard Aoun

In this paper we show that for every congruent monotileable amenable group $G$ and for every metrizable Choquet simplex $K$, there exists a minimal $G$-subshift, which is free on a full measure set, whose set of invariant probability…

Dynamical Systems · Mathematics 2017-09-26 Paulina Cecchi , María Isabel Cortez

We provide the first examples of finitely generated simple groups that are amenable (and infinite). This follows from a general existence result on invariant states for piecewise-translations of the integers. The states are obtained by…

Group Theory · Mathematics 2012-05-01 Kate Juschenko , Nicolas Monod

We prove that there exists a group which is not finitely generated, but admits a minimal sofic shift. This answers a question of Doucha, Melleray and Tsankov. The group is of the form $(F_4 \times F_2) \rtimes F_{\infty}$. The construction…

Dynamical Systems · Mathematics 2025-07-10 Ville Salo

We prove that every finitely generated soluble group which is not virtually abelian has a subgroup of one of a small number of types.

Group Theory · Mathematics 2015-10-09 Tara Brough , Derek Holt

We show that any action of a finite group on a finitely presentable group arises as the action of the group of self-homotopy equivalences of a space on its fundamental group. In doing so, we prove that any finite connected (abstract)…

Algebraic Topology · Mathematics 2025-09-23 Cristina Costoya , Rafael Gomes , Antonio Viruel