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Graph independence (also known as $\epsilon$-independence or $\lambda$-independence) is a mixture of classical independence and free independence corresponding to graph products or groups and operator algebras. Using conjugation by certain…

Building on recent work of Robertson and Steger, we associate a C*-algebra to a combinatorial object which may be thought of as a higher rank graph. This C*-algebra is shown to be isomorphic to that of the associated path groupoid.…

Operator Algebras · Mathematics 2007-05-23 Alex Kumjian , David Pask

In this paper we define a way to get a bounded invertible automaton starting from a finite graph. It turns out that the corresponding automaton group is regular weakly branch over its commutator subgroup, contains a free semigroup on two…

Group Theory · Mathematics 2021-06-10 Matteo Cavaleri , Daniele D'Angeli , Alfredo Donno , Emanuele Rodaro

We describe the development of the theory of automatic groups. We begin with a historical introduction, define the concepts of automatic, biautomatic and combable groups, derive basic properties, then explain how hyperbolic groups and the…

Group Theory · Mathematics 2022-05-31 Sarah Rees

We prove that, to every abstract group $G$, we can associate a sequence of graphs $\Gamma_n$ such that the automorphism group of $\Gamma_n$ is isomorphic to $G$ and the genus of $\Gamma_n$ is an unbounded function of $n$.

Group Theory · Mathematics 2025-08-29 Marco Barbieri

In this paper we identify different classes of free group extension using core graphs. We show that every free group extension $H\leq K\leq F$ has a base $B$ such that the associated pointed graph morphism…

Group Theory · Mathematics 2020-11-25 Noam M. D. Kolodner

The classical notion of a k-automatic subset of the natural numbers is here extended to that of an F-automatic subset of an arbitrary finitely generated abelian group $\Gamma$ equipped with an arbitrary endomorphism F. This is applied to…

Number Theory · Mathematics 2019-07-10 Jason Bell , Rahim Moosa

We study centralisers of finite order automorphisms of generalisations of Thompson's group F and conjugacy classes of finite subgroups in finite extensions of these groups. In particular, we show that centralisers of finite automorphisms in…

Group Theory · Mathematics 2010-02-10 D. H. Kochloukova , C. Martínez-Pérez , B. E. A. Nucinkis

A graph $\Gamma$ labelled by a set $S$ defines a group $G(\Gamma)$ whose generators are the set of labels $S$ and whose relations are all words which can be read on closed paths of this graph. We introduce the notion of aspherical graph and…

Group Theory · Mathematics 2022-06-17 Vadim Bereznyuk

We investigate fixed-point properties of automorphisms of groups similar to R. Thompson's group $F$. Revisiting work of Gon\c{c}alves-Kochloukova, we deduce a cohomological criterion to detect infinite fixed-point sets in the…

We construct a family of groups from suitable higher rank graphs which are analogues of the finite symmetric groups. We introduce homological invariants showing that many of our groups are, for example, not isomorphic to $nV$, when $n \geq…

Group Theory · Mathematics 2023-02-28 Mark V Lawson , Aidan Sims , Alina Vdovina

We introduce forest diagrams to represent elements of Thompson's group F. These diagrams relate to a certain action of F on the real line in the same way that tree diagrams relate to the standard action of F on the unit interval. Using…

Group Theory · Mathematics 2018-10-30 James M. Belk , Kenneth S. Brown

Let us say that a Cayley graph $\Gamma$ of a group $G$ of order $n$ is a Cerny Cayley graph if every synchronizing automaton containing $\Gamma$ as a subgraph with the same vertex set admits a synchronizing word of length at most $(n-1)^2$.…

Combinatorics · Mathematics 2008-08-12 Benjamin Steinberg

The purpose of this paper is to study the properties of the irrational-slope Thompson's group $F_\tau$ introduced by Cleary in 1995. We construct presentations, both finite and infinite and we describe its combinatorial structure using…

Group Theory · Mathematics 2021-03-04 José Burillo , Brita Nucinkis , Lawrence Reeves

We describe standard forms for elements of the higher-dimensional Thompson groups $nV$ arising from gridding subdivision processes. These processes lead to standard normal form descriptions for elements in these groups, and sizes of these…

Group Theory · Mathematics 2024-03-06 José Burillo , Sean Cleary , Brita Nucinkis

In this paper we give a new generalization of token graphs. Given two integers $1\leq m \leq k$ and a graph $G$ we define the generalized token graph of the graph $G$, to be the graph $F_k^m(G)$ whose vertices correspond to configurations…

Combinatorics · Mathematics 2025-09-03 C. Amairani Herrera-Ramirez , Teresa I. Hoekstra-Mendoza

If $G$ is a finitely generated group and $X$ is a Cayley graph of $G$, denote by $\mathcal{C}_1^X(G)$ the subgroup of all automorphisms of $X$ commensurating $G$ and fixing the vertex corresponding to the identity. Building on the work of…

Group Theory · Mathematics 2025-07-16 Dominik Francoeur

We study automaton structures, i.e. groups, monoids and semigroups generated by an automaton, which, in this context, means a deterministic finite-state letter-to-letter transducer. Instead of considering only complete automata, we…

Formal Languages and Automata Theory · Computer Science 2020-07-17 Daniele D'Angeli , Emanuele Rodaro , Jan Philipp Wächter

We consider a class of groups $V_n(G)$ which are supergroups of the Higman-Thompson groups $V_n$. These groups fit in a framework of Elizabeth Scott for generating infinite virtually simple groups, and the groups we study in particular are…

Group Theory · Mathematics 2014-12-18 Collin Bleak , Casey Donoven , Julius Jonušas

The recently introduced A-homotopy groups for graphs are investigated. The main concern of the present article is the construction of an infinite cell complex, the homotopy groups of which are isomorphic to the A-homotopy groups of the…

Combinatorics · Mathematics 2007-05-23 E. Babson , H. Barcelo , M. de Longueville , R. Laubenbacher