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The structure of finite and locally finite groups in which every element has prime power order (CP-groups) is well known. In this paper we note that the combination of our earlier results with the available information on the structure of…

Group Theory · Mathematics 2020-01-07 Pavel Shumyatsky

We introduce the concept of cyclicity and hypercyclicity in self-similar groups as an analogue of cyclic and hypercyclic vectors for an operator on a Banach space. We derive a sufficient condition for cyclicity of non-finitary automorphisms…

Group Theory · Mathematics 2026-01-29 Jorge Fariña-Asategui

A profinite group equipped with an expansive endomorphism is equivalent to a one-sided group shift. We show that these groups have a very restricted structure. More precisely, we show that any such group can be decomposed into a finite…

Dynamical Systems · Mathematics 2020-08-04 Michael Wibmer

We show that a free action $G \curvearrowright X$ is almost finite if its restriction to some infinite normal subgroup of $G$ is almost finite. Consider the class of groups which contains all infinite groups of locally subexponential growth…

Dynamical Systems · Mathematics 2023-06-01 Petr Naryshkin

We study abstract finite groups with the property, called property $\hat{s}$, that all of their subrepresentations have submultiplicative spectra. Such groups are necessarily nilpotent and we focus on $p$-groups. $p$-groups with property…

Group Theory · Mathematics 2011-10-19 L. Grunenfelder , T. Košir , M. Omladič , H. Radjavi

We construct the first examples of infinite sharply 2-transitive groups which are finitely generated. Moreover, we construct such a group that has Kazhdan property (T), is simple, has exactly four conjugacy classes, and we show that this…

Group Theory · Mathematics 2024-11-20 Simon André , Vincent Guirardel

Let $w$ be a multilinear commutator word. In the present paper we describe recent results that show that if $G$ is a profinite group in which all $w$-values are contained in a union of finitely (or in some cases countably) many subgroups…

Group Theory · Mathematics 2017-03-06 Cristina Acciarri , Pavel Shumyatsky

We generalise a technical tool, originally developed by Pervova for the study of maximal subgroups in Grigorchuk and GGS groups, to all weakly branch groups satisfying a natural condition, and in particular to all branch groups. We then use…

Group Theory · Mathematics 2020-04-06 Dominik Francoeur

We give another proof for a result of Brick stating that the simple connectivity at infinity is a geometric property of finitely presented groups. This allows us to define the rate of vanishing of $\p1i$ for those groups which are simply…

Geometric Topology · Mathematics 2007-05-23 Louis Funar , Daniele Ettore Otera

We show that a profinite completion functor for (simplicial or topological) operads with good homotopical properties can be constructed as a left Quillen functor from an appropriate model category of infinity-operads to a certain model…

Algebraic Topology · Mathematics 2021-07-22 Thomas Blom , Ieke Moerdijk

We say a group is finitely annihilated if it is the set-theoretic union of all its proper normal finite index subgroups. We investigate this new property, and observe that it is independent of several other well known group properties. For…

Group Theory · Mathematics 2019-02-20 Maurice Chiodo

A soluble pro-p group of finite rank is finitely axiomatizable in the class of all profinite groups if and only if for each open subgroup H, the image of Z(H) in the abelianization of H is finite, subject to some suitable hypothesis of…

Group Theory · Mathematics 2023-03-28 Dan Segal

We identify natural conditions for a countable group acting on a countable tree which imply that the orbit equivalence relation of the induced action on the Gromov boundary is Borel hyperfinite. Examples of this condition include…

Group Theory · Mathematics 2025-07-10 Srivatsav Kunnawalkam Elayavalli , Koichi Oyakawa , Forte Shinko , Pieter Spaas

We prove that certain Fuchsian triangle groups are profinitely rigid in the absolute sense, i.e. each is distinguished from all other finitely generated, residually finite groups by its set of finite quotients. We also develop a method…

Group Theory · Mathematics 2021-10-04 M. R. Bridson , D. B. McReynolds , A. W. Reid , R. Spitler

We prove:(1) the existence, for every integer n > 3, of a noncompact smooth n-dimensional topological manifold whose diffeomorphism group contains an isomorphic copy of every finitely presented group; (2) a finiteness theorem on finite…

Group Theory · Mathematics 2014-01-07 Vladimir L. Popov

If a finite group G has a presentation with d generators and r relations, it is well-known that r - d is at least the rank of the Schur multiplier of G; a presentation is called efficient if equality holds. There is an analogous definition…

Group Theory · Mathematics 2009-05-05 R. M. Guralnick , W. M. Kantor , M. Kassabov , A. Lubotzky

A group word $w$ is said to be strongly concise in a class $\mathcal{C}$ of profinite groups if, for every group $G$ in $\mathcal{C}$ such that $w$ takes less than $2^{\aleph_0}$ values in $G$, the verbal subgroup $w(G)$ is finite. Detomi,…

Group Theory · Mathematics 2020-05-27 Eloisa Detomi , Benjamin Klopsch , Pavel Shumyatsky

In previous articles, we showed that the category of profinite $L$-algebras (where $L$ is a normal modal logic with the finite model property) is monadic over $\textbf{Set}$. Then, we developed sequent calculi for extensions of the language…

Logic · Mathematics 2025-09-17 Matteo De Berardinis

A topological group G is profinite if it is compact and totally disconnected. Equivalently, G is the inverse limit of a surjective system of finite groups carrying the discrete topology. We discuss how to represent a countably based…

Group Theory · Mathematics 2019-02-08 Andre Nies

Let $p$ be a prime number, and let $k$ be an algebraically closed field of characteristic $p$. We show that the tame fundamental group of a smooth affine curve over $k$ is a projective profinite group. We prove that the fundamental group of…

Algebraic Geometry · Mathematics 2021-03-09 Hélène Esnault , Mark Shusterman , Vasudevan Srinivas