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We show that every Coxeter group that is not virtually abelian and for which all labels in the corresponding Coxeter graph are powers of 2 or infinity can be mapped onto uncountably many infinite 2-groups which, in addition, may be chosen…

Group Theory · Mathematics 2009-12-16 R. Grigorchuk

Given a countable abelian group $A$, we construct a row finite directed graph $\Gamma(A)$ such that the $K_{0}$-group of the graph $\textrm{C}^{\ast}$-algebra $\textrm{C}^{\ast}(\Gamma(A))$ is canonically isomorphic to $A$. Moreover, each…

Operator Algebras · Mathematics 2025-12-23 Swarnendu Datta , Debashish Goswami , Soumalya Joardar

We give a simpler proof using automata theory of a recent result of Kapovich, Weidmann and Myasnikov according to which so-called benign graphs of groups preserve decidability of the generalized word problem. These include graphs of groups…

Group Theory · Mathematics 2009-05-28 Markus Lohrey , Benjamin Steinberg

We show that if $G$ is a group and $G$ has a graph-product decomposition with finitely-generated abelian vertex groups, then $G$ has two canonical decompositions as a graph product of groups: a unique decomposition in which each vertex…

Group Theory · Mathematics 2019-02-07 Mauricio Gutierrez , Adam Piggott

We compute explicitly the automorphism and outer automorphism group of all large-type free-of-infinity Artin groups. Our strategy involves reconstructing the associated Deligne complexes in a purely algebraic manner, i.e. in a way that is…

Group Theory · Mathematics 2024-10-15 Nicolas Vaskou

This article initiates a geometric study of the automorphism groups of general graph products of groups, and investigates the algebraic and geometric structure of automorphism groups of cyclic product of groups. For a cyclic product of at…

Group Theory · Mathematics 2018-03-21 Anthony Genevois , Alexandre Martin

In this article, we consider qualified notions of geometric finiteness in mapping class groups called parabolically geometrically finite (PGF) and reducibly geometrically finite (RGF). We examine several constructions of subgroups and…

Geometric Topology · Mathematics 2025-09-16 Tarik Aougab , Harrison Bray , Spencer Dowdall , Hannah Hoganson , Sara Maloni , Brandis Whitfield

Barbieri recently showed that the finite graphs realising any given finite automorphism group have unbounded genus, answering a question of Cornwell et al. In this note we give a short proof of a stronger result: they have unbounded clique…

Combinatorics · Mathematics 2025-01-20 John Haslegrave

We define an integer-valued invariant of special cube complexes called the genus, and prove that having genus one characterizes special cube complexes with abelian fundamental group. Using the genus, we obtain a new proof that the…

Geometric Topology · Mathematics 2016-12-30 Corey Bregman

In the present paper, we study the outer automorphism groups of the absolute Galois groups of mixed-characteristic local fields from the point of view of anabelian geometry. In particular, we show that, under certain mild assumptions, the…

Number Theory · Mathematics 2025-12-15 Kaiji Kondo

In this paper, we prove several results on finitely generated dynamical Galois groups attached to quadratic polynomials. First we show that, over global fields, quadratic post-critically finite polynomials are precisely those having an…

Number Theory · Mathematics 2020-08-26 Andrea Ferraguti , Carlo Pagano

We classify two-dimensional right-angled Coxeter groups that are quasiisometric to a right-angled Artin group defined by a tree, and show that when this is true the right-angled Coxeter group actually contains a visible finite index…

Group Theory · Mathematics 2025-11-12 Christopher H. Cashen

For G, H two finite collections of finitely generated subgroups of a right-angled Artin group A, the untwisted McCool group U(A; G, Ht) is the subgroup of untwisted outer automorphisms of A preserving the conjugacy class of each element of…

Group Theory · Mathematics 2025-03-13 Adrien Abgrall

The Resolution Theorem for Compact Abelian Groups is applied to show that the profinite subgroups of a finite-dimensional compact connected abelian group (protorus) which induce tori quotients comprise a lattice under intersection (meet)…

Group Theory · Mathematics 2025-03-28 Wayne Lewis

We investigate the minimal genus problem for the second homology of a right angled Artin group (RAAG). Firstly, we present a lower bound for the minimal genus of a second homology class, equal to half the rank of the corresponding cap…

Geometric Topology · Mathematics 2023-12-12 Rachael Boyd , Thorben Kastenholz , Jean Pierre Mutanguha

We prove that the outer automorphism group $\mathrm{Out}(N)$ of an infinitely generated free nilpotent group $N$ of class two is complete.

Group Theory · Mathematics 2025-05-20 Vladimir A. Tolstykh

We prove that the topological full group $[[X]]$ of a two-sided full shift $X = \Sigma^{\mathbb{Z}}$ contains every right-angled Artin group (also called a graph group). More generally, we show that the family of subgroups with "linear…

Group Theory · Mathematics 2021-03-12 Ville Salo

For each countable group $Q$ we produce a short exact sequence $1\to N \to G \to Q\to 1$ where $G$ is f.g. and has a graphical $\frac16$ presentation and $N$ is f.g. and satisfies property $T$. As a consequence we produce a group $N$ with…

Group Theory · Mathematics 2007-05-23 Yann Ollivier , Daniel T. Wise

We extend the characterization of stable subgroups of right-angled Artin groups of Koberda, Mangahas and Taylor to the case of graph products of infinite groups. Specifically, we show that the stable subgroups of such graph products are…

Group Theory · Mathematics 2026-04-01 Sahana H Balasubramanya , Marissa Chesser , Alice Kerr , Johanna Mangahas , Marie Trin

It is shown, for a given graph group $G$, that the fixed point subgroup Fix$\,\varphi$ is finitely generated for every endomorphism $\varphi$ of $G$ if and only if $G$ is a free product of free abelian groups. The same conditions hold for…

Group Theory · Mathematics 2013-10-29 Emanuele Rodaro , Pedro V. Silva , Mihalis Sykiotis