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We study the conjugacy problem in cyclic extensions of free groups. It is shown that the conjugacy problem is solvable in split extensions of finitely generated free groups by virtually inner automorphisms. An algorithm for construction of…

Group Theory · Mathematics 2007-05-23 Valerij Bardakov , Leonid Bokut , Andrei Vesnin

The main result of this paper is that the outer automorphism group of a free product of finite groups and cyclic groups is semistable at infinity (provided it is one ended) or semistable at each end. In a previous paper, we showed that the…

Group Theory · Mathematics 2025-03-10 Rylee Alanza Lyman

We prove that there exist finitely presented, residually finite groups that are profinitely rigid in the class of all finitely presented groups but not in the class of all finitely generated groups. These groups are of the form $\Gamma…

Group Theory · Mathematics 2025-04-15 M. R. Bridson , A. W. Reid , R. Spitler

We prove the pro-supersolvable closure of a finitely generated subgroup of the free group is finitely generated. It extends similar results for pro-$p$ closures proved by Ribes-Zalesskii and pro-Nilpotent closures proved by…

Group Theory · Mathematics 2022-09-20 Lida Chen , Jianchun Wu

We prove that an automorphism $\phi:F\to F$ of a finitely generated free group $F$ is hyperbolic in the sense of Gromov if it has no nontrivial periodic conjugacy classes.

Group Theory · Mathematics 2007-05-23 Peter Brinkmann

We present a solution to the Conjugacy Problem in the group of outer-automorphisms of $F_3$, a free group of rank 3. We distinguish according to several computable invariants, such as irreducibility, subgroups of polynomial growth, and…

Group Theory · Mathematics 2025-06-09 François Dahmani , Stefano Francaviglia , Armando Martino , Nicholas Touikan

We give two examples of a finitely generated subgroup of a free group and a subset, closed in the profinite topology of a free group, such that their product is not closed in the profinite topology of a free group.

Group Theory · Mathematics 2017-09-20 Rita Gitik , Eliyahu Rips

In this paper we study the residual solvability of the generalized free product of finitely generated nilpotent groups. We show that these kinds of structures are often residually solvable.

Group Theory · Mathematics 2007-05-23 D. Kahrobaei

We show that an accessible group with infinitely many ends has property $R_{\infty}$. That is, it has infinitely many twisted conjugacy classes for any twisting automorphism. We deduce that having property $R_{\infty}$ is undecidable…

Group Theory · Mathematics 2026-03-02 Francesco Fournier-Facio , Harry Iveson , Armando Martino , Wagner Sgobbi , Peter Wong

If F is a surface with boundary, then a finitely generated subgroup without peripheral elements of G = {\pi}_1(F) can be separated from finitely many other elements of G by a finite index subgroup of G corresponding to a finite cover F'…

Geometric Topology · Mathematics 2014-10-01 Mark D. Baker , Daryl Cooper

We prove that if a conjugation quandle is Hopfian, then its underlying group is also Hopfian. We also show that the converse does not hold by providing an example. This highlights a distinction between conjugation quandles and their…

Geometric Topology · Mathematics 2025-09-18 Mohamed Elhamdadi , Jan Kim

We construct a finitely generated residually finite group $G$ with the property that every finite index subgroup of $G$ contains a subgroup isomorphic to Promislow's group. Hence $G$ does not have a finite index subgroup with the unique…

Group Theory · Mathematics 2026-02-13 Naomi Bengi , Daniel T. Wise

We establish {\em{virtual surjection to pairs}} (VSP) as a general criterion for the finite presentability of subdirect products of groups: if $\Gamma_1,...,\Gamma_n$ are finitely presented and $S<\Gamma_1\times...\times\Gamma_n$ projects…

Group Theory · Mathematics 2025-07-16 Martin R. Bridson , James Howie , Charles F. Miller , Hamish Short

We prove that every subnormal subgroup of p-power index in a right-angled Artin group is conjugacy p-separable. As an application, we prove that every right-angled Artin group is conjugacy separable in the class of torsion-free nilpotent…

Group Theory · Mathematics 2013-03-05 Emmanuel Toinet

We construct the first example of a finitely-presented, residually-finite group that contains an infinite sequence of non-isomorphic finitely-presented subgroups such that each of the inclusion maps induces an isomorphism of profinite…

Group Theory · Mathematics 2015-01-08 Martin R. Bridson

In this paper we consider the {\em conjugacy stability} property of subgroups and provide effective procedures to solve the problem in several classes of groups. In particular, we start with free groups, that is, we give an effective…

Group Theory · Mathematics 2021-07-14 Isabel Fernández Martínez , Denis Serbin

We construct a class of finitely generated groups which have arbitrarily large conjugacy separability function, but in which the conjugacy problem can be solved in polynomial time, demonstrating that the McKinsey algorithm for the conjugacy…

Group Theory · Mathematics 2025-04-17 Lukas Vandeputte

We prove that every finitely generated, residually finite group $G$ embeds into a finitely generated perfect branch group $\Gamma$ such that many properties of $G$ are preserved under this embedding. Among those are the properties of being…

Group Theory · Mathematics 2024-03-06 Steffen Kionke , Eduard Schesler

We show that the compressed word problem in a finitely-generated fully residually free group (F -group) is decidable in polynomial time, and use the result to show that the word problem in the automorphism group of such a group is decidable…

Group Theory · Mathematics 2009-10-21 Jeremy Macdonald

We prove that all finitely generated fully residually free groups (limit groups) have a sequence of finite dimensional unitary representations that `strongly converge' to the regular representation of the group. The corresponding statement…

Group Theory · Mathematics 2023-01-18 Larsen Louder , Michael Magee with Appendix by Will Hide , Michael Magee