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We show that pseudo-Anosov mapping classes are generic in every Cayley graph of the mapping class group of a finite-type hyperbolic surface. Our method also yields an analogous result for rank-one CAT(0) groups and hierarchically hyperbolic…

Geometric Topology · Mathematics 2025-10-21 Inhyeok Choi

A random group contains many subgroups which are isomorphic to the fundamental group of a compact hyperbolic 3-manifold with totally geodesic boundary. These subgroups can be taken to be quasi-isometrically embedded. This is true both in…

Group Theory · Mathematics 2017-02-23 Danny Calegari , Henry Wilton

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 characterize the groups isomorphic to full automorphism groups of ordered abelian groups. The result will follow from classical theorems on ordered groups adding an argument from proofs used to realize rings as endomorphism rings of…

Logic · Mathematics 2007-05-23 Rüdiger Göbel , Saharon Shelah

For a subshift over a finite alphabet, a measure of the complexity of the system is obtained by counting the number of nonempty cylinder sets of length $n$. When this complexity grows exponentially, the automorphism group has been shown to…

Dynamical Systems · Mathematics 2014-03-04 Van Cyr , Bryna Kra

It has been proven by Schupp and Bergman that the inner automorphisms of groups can be characterized purely categorically as those group automorphisms that can be coherently extended along any outgoing homomorphism. One is thus motivated to…

Category Theory · Mathematics 2021-07-30 Jason Parker

We show that the automorphism groups of countably categorical linear orders are extremely amenable. Using methods of Kechris, Pestov, and Todorcevic, we use this fact to derive a structural Ramsey theorem for certain families of finite…

Logic · Mathematics 2014-02-17 François G. Dorais , Steven Gubkin , Daniel McDonald , Manuel Rivera

We adapt a proof of Lascar in order to show the simplicity of the group of automorphisms fixing pointwise all non-generic elements for a class of uncountable models of suitable theories, encompassing both strongly minimal theories as well…

We prove that the outer automorphism group of a free group of countably infinite rank is complete.

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

By recognizing them as fundamental groups of developable complexes of groups we prove that mapping class groups of compact orientable surfaces have finite asymptotic dimension.

Group Theory · Mathematics 2008-01-22 Gregory C. Bell , Alexander Dranishnikov

We show that if $G$ is a non-elementary word hyperbolic group, mapping class group of a hyperbolic surface or the outer automorphism group of a nonabelian free group then $G$ has $2^{\aleph_0}$ many continuous ergodic invariant random…

Group Theory · Mathematics 2015-06-02 Lewis Bowen , Rostislav Grigorchuk , Rostyslav Kravchenko

For each of the 14 classes of edge-transitive maps described by Graver and Watkins, necessary and sufficient conditions are given for a group to be the automorphism group of a map, or of an orientable map without boundary, in that class.…

Combinatorics · Mathematics 2019-06-26 Gareth A. Jones

This is Chapter 24 in the "AutoMathA" handbook. Finite automata have been used effectively in recent years to define infinite groups. The two main lines of research have as their most representative objects the class of automatic groups…

Formal Languages and Automata Theory · Computer Science 2015-03-17 Laurent Bartholdi , Pedro V. Silva

We determine the structure of automorphism groups of finite graphs of bounded Hadwiger number. Our proof includes a structural analysis of finite edge-transitive graphs. In particular, we show that for connected, $K_{h+1}$-minor-free,…

Combinatorics · Mathematics 2025-09-24 Martin Grohe , Pascal Schweitzer , Daniel Wiebking

With the help of the theory of holomorphic and anti-holomorphic differentials, G. A. Jones [Chiral covers of hypermaps, Ars Math. Contemp. 8 (2015), 425-431] proved that every regular hypermap of a non-spherical type is covered by an…

Group Theory · Mathematics 2024-02-23 Olivia Reade , Jozef Širáň

Suppose that a finitely generated group $G$ is hyperbolic relative to a collection of subgroups $\{H_1, ..., H_m\} $. We prove that if each of the subgroups $H_1, ..., H_m$ has finite asymptotic dimension, then asymptotic dimension of $G$…

Group Theory · Mathematics 2007-05-23 D. V. Osin

We prove that every orientable infinite type surface without boundary and finite genus has a Riemann surface structure such that its modular group of quasiconformal homeomorphisms is countable.

Geometric Topology · Mathematics 2024-08-26 Rogelio Niño Hernández

By an automorphism of a topological group G we mean an isomorphism of G onto itself which is also a homeomorphism. In this article, we study the automorphism group Aut(G) of a dense subgroup G of R^n, n>=1. We show that Aut(G) can be…

Group Theory · Mathematics 2019-12-11 Vitalij Chatyrko , Dmitri Shakhmatov

We consider automorphism groups of some countably categorical structures and their precompact expansions. We prove that automorphism groups of omega-stable omega-categorical structures have metrizable universal minimal flows. We also study…

Logic · Mathematics 2014-12-23 Aleksander Ivanov

We show that the number of twisted conjugacy classes is infinite for any automorphism of non-elementary, Gromov hyperbolic group . An analog of Selberg theory for twisted conjugacy classes is proposed.

Group Theory · Mathematics 2007-05-23 Alexander Fel'shtyn