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We introduce the class of strongly sofic monoids. This class of monoids strictly contains the class of sofic groups and is a proper subclass of the class of sofic monoids. We define and investigate sofic topological entropy for actions of…

Group Theory · Mathematics 2025-02-10 Tullio Ceccherini-Silberstein , Michel Coornaert , Xuan Kien Phung

Let $\mathcal{S}$ be a sequence of finite perfect transitive permutation groups with uniformly bounded number of generators. We prove that the infinitely iterated wreath product in product action of the groups in $\mathcal{S}$ is…

Group Theory · Mathematics 2016-03-18 Matteo Vannacci

We classify $\mathcal{R}$- and $\mathcal{L}$-cross-sections of wreath products of finite inverse symmetric semigroups $\mathcal{IS}_m \wr_p \mathcal{IS}_n$ up to isomorphism. We show that every isomorphism of $\mathcal{R}$ ($\mathcal{L}$-)…

Group Theory · Mathematics 2020-06-30 Eugenia Kochubinska

We show that a group acting on a non-trivial tree with finite edge stabilizers and icc vertex stabilizers admits a faithful and highly transitive action on an infinite countable set. This result is actually true for infinite vertex…

Group Theory · Mathematics 2013-04-16 Pierre Fima , Soyoung Moon , Yves Stalder

We prove that any Lie subgroup $G$ (with finitely many connected components) of an infinite-dimensional topological group $\mathcal G$ which is an amalgamated product of two closed subgroups, can be conjugated to one factor. We apply this…

Complex Variables · Mathematics 2022-02-01 Frank Kutzschebauch , Andreas Lind

We introduce and study soficity for Lie algebras, modelled after linear soficity in associative algebras. We introduce equivalent definitions of soficity, one involving metric ultraproducts and the other involving almost representations. We…

Rings and Algebras · Mathematics 2022-03-14 Cameron Cinel

We show that group actions on many treelike compact spaces are not too complicated dynamically. We first observe that an old argument of Seidler implies that every action of a topological group $G$ on a regular continuum is null and…

Dynamical Systems · Mathematics 2019-06-05 Eli Glasner , Michael Megrelishvili

Groups with a large $p$-subgroup, $p$ a prime, include almost all of the groups of Lie type in characteristic $p$ and so the study of such groups adds to our understanding of the finite simple groups. In this article we study a special…

Group Theory · Mathematics 2019-06-19 Chris Parker , Gernot Stroth

Some well-known and less well-known or new notions related to group actions are surveyed. Some of these notions are used to generalize affine spaces. Actions are seen as functions with values in transformation monoids

Group Theory · Mathematics 2016-11-18 Dan Jonsson

We prove that each \omega-categorical, generically stable group is solvable-by-finite.

Logic · Mathematics 2023-11-14 Jan Dobrowolski , Krzysztof Krupinski

We give a complete characterization of Hamiltonian actions of compact Lie groups on exact symplectic manifolds with proper momentum maps. We deduce that every Hamiltonian action of a compact Lie group on a contractible symplectic manifold…

Symplectic Geometry · Mathematics 2016-07-14 Yael Karshon , Fabian Ziltener

In this paper, we show that wreath products of groups have linear divergence, and we generalise the argument to permutational wreath products. We also prove that Houghton groups $\mathcal{H}_m$ with $m\geq 2$ and Baumslag-Solitar groups…

Group Theory · Mathematics 2025-12-16 Letizia Issini

In this paper, we present generalizations of some results on the asymptotic property C for wreath products. Specifically, we prove that certain wreath-like products admit asymptotic property C, thus providing some new examples for further…

Group Theory · Mathematics 2025-12-09 Han Liu

We establish obstructions for groups to act by homeomorphisms on dendrites. For instance, lattices in higher rank simple Lie groups will always fix a point or a pair. The same holds for irreducible lattices in products of connected groups.…

Dynamical Systems · Mathematics 2021-04-21 Bruno Duchesne , Nicolas Monod

In analogy to the disjoint cycle decomposition in permutation groups, Ore and Specht define a decomposition of elements of the full monomial group and exploit this to describe conjugacy classes and centralisers of elements in the full…

Group Theory · Mathematics 2021-11-29 Dominik Bernhardt , Alice C. Niemeyer , Friedrich Rober , Lucas Wollenhaupt

The main purpose of this paper is to strengthen our understanding of sofic mean dimension of two typical classes of sofic group actions. First, we study finite group actions. We prove that sofic mean dimension of any amenable group action…

Dynamical Systems · Mathematics 2026-02-27 Lei Jin , Yixiao Qiao

We show that any free product of two countable groups, one of them being infinite, admits a faithful and homogeneous action on the Random Graph. We also show that a large class of HNN extensions or free products, amalgamated over a finite…

Group Theory · Mathematics 2021-05-26 Pierre Fima , Soyoung Moon , Yves Stalder

We study simplicial action of groups on one vertex Kan complexes. We show that every semi-direct product of the fundamental group of an one vertex Kan complex with a finite group can be simplicially realized. We also calculate the…

Algebraic Topology · Mathematics 2013-08-15 Goutam Mukherjee , Swagata Sarkar , Debasis Sen

Given an action of a groupoid by isomorphisms on a Fell bundle (over another groupoid), we form a semidirect-product Fell bundle, and prove that its $C^{*}$-algebra is isomorphic to a crossed product.

Operator Algebras · Mathematics 2021-12-30 Lucas Hall , S. Kaliszewski , John Quigg , Dana P. Williams

We prove that globally F-regular $F$-sandwiches of degree $p$ of a projective space are toric varieties.

Algebraic Geometry · Mathematics 2016-04-05 Tadakazu Sawada