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We generalize a well known periodicity lemma from the case of free groups to the case of acylindrically hyperbolic groups. This generalization will be used later to describe solutions of certain equations in acylindrically hyperbolic groups…

Group Theory · Mathematics 2019-03-06 Oleg Bogopolski

We consider groups of the form $G=AB$ with two locally cyclic subgroups $A$ and $B$. The structure of these groups is determined in the cases when $A$ and $B$ are both periodic or when one of them is periodic and the other is not. Together…

Group Theory · Mathematics 2020-09-09 Bernhard Amberg , Yaroslav Sysak

We show that the group $\langle a,b,c,t : a^t=b,b^t=c,c^t=ca^{-1} \rangle$ is profinitely rigid amongst free-by-cyclic groups, providing the first example of a hyperbolic free-by-cyclic group with this property.

Group Theory · Mathematics 2025-08-06 Naomi Andrew , Paige Hillen , Robert Alonzo Lyman , Catherine Eva Pfaff

We investigate which free constructions (amalgamated products and HNN-extensions) over word hyperbolic groups produce groups that are again word hyperbolic. A complete answer is obtained for the case when the amalgamated subgroups are…

Group Theory · Mathematics 2008-02-03 Olga Kharlampovich , Alexey Myasnikov

The topology of the Bowditch boundary of a relatively hyperbolic group pair gives information about relative splittings of the group. It is therefore interesting to ask if there is generic behavior of this boundary. The purpose of this…

Group Theory · Mathematics 2023-10-13 Aaron W. Messerla

This paper describes some generalizations of the results presented in the book "Geometry of defining Relations in Groups" , of A.Yu.Ol'shanskii to the case of non-cyclic torsion-free hyperbolic groups. In particular, it is proved that for…

Group Theory · Mathematics 2022-08-08 Olga Kulikova

We show that in general for a given group the structure of a maximal hyperbolic tower over a free group is not canonical: We construct examples of groups having hyperbolic tower structures over free subgroups which have arbitrarily large…

Group Theory · Mathematics 2021-07-01 Benjamin Brück

We prove that hyperbolic groups with logarithmic separation profiles split over cyclic groups. This shows that such groups can be inductively built from Fuchsian groups and free groups by amalgamations and HNN extensions over finite or…

Group Theory · Mathematics 2025-03-12 Nir Lazarovich , Corentin Le Coz

We describe an algorithm which determines whether or not a group which is hyperbolic relative to abelian groups admits a nontrivial splitting over a finite group.

Group Theory · Mathematics 2009-03-19 Francois Dahmani , Daniel Groves

We show that the theory of the free group -- and more generally the theory of any torsion-free hyperbolic group -- is $n$-ample for any $n\geq 1$. We give also an explicit description of the imaginary algebraic closure in free groups.

Group Theory · Mathematics 2012-05-15 Abderezak Ould Houcine , Katrin Tent

This paper is devoted to the proof of the property of order separability for free product of free groups with maximal cyclic amalgamated subgroups.

Group Theory · Mathematics 2010-07-09 Vladimir V. Yedynak

We prove that every free metabelian non--cyclic group has a finitely generated isolated subgroup which is not separable in the class of nilpotent groups. As a corollary we prove that for every prime number $p$ an arbitrary free metabelian…

Group Theory · Mathematics 2007-05-23 Valerij G. Bardakov

We give an example of a definable set in every free or torsion-free (non-elementary) hyperbolic group that is not in the Boolean algebra of equational sets. Hence, the theories of free and torsion-free (non-elementary) hyperbolic groups are…

Logic · Mathematics 2012-04-24 Z. Sela

Let $D$ be a weakly locally finite division ring and $n$ a positive integer. In this paper, we investigate the problem on the existence of non-cyclic free subgroups in non-central almost subnormal subgroups of the general linear group ${\rm…

Rings and Algebras · Mathematics 2016-02-12 Nguyen Kim Ngoc , Mai Hoang Bien , Bui Xuan Hai

Let $K$ be a field and let $\sigma$ be an automorphism and let $\delta$ be a $\sigma$-derivation of $K$. Then we show that the multiplicative group of nonzero elements of the division ring $D=K(x;\sigma,\delta)$ contains a free non-cyclic…

Rings and Algebras · Mathematics 2018-12-06 Jason P. Bell , Jairo Goncalves

We construct a non-free but aleph_1-separable, torsion-free abelian group G with a pure free subgroup B such that all subgroups of G disjoint from B are free and such that G/B is divisible. This answers a question of Irwin and shows that a…

Logic · Mathematics 2007-11-21 Andreas Blass , Saharon Shelah

Consider a one-ended word-hyperbolic group. If it is the fundamental group of a graph of free groups with cyclic edge groups then either it is the fundamental group of a surface or it contains a finitely generated one-ended subgroup of…

Group Theory · Mathematics 2014-11-11 Henry Wilton

We give necessary and sufficient conditions for a free-by-free group to be relatively hyperbolic with a cusp-preserving structure. Namely, if $\phi_1, \ldots , \phi_k $ is a collection of exponentially growing outer automorphisms with a…

Group Theory · Mathematics 2025-08-25 Pritam Ghosh , Funda Gültepe

We prove that cyclic subgroup separability is preserved under exponential completion for groups that belong to a class that includes all coherent RAAGs and toral relatively hyperbolic groups; we do so by exploiting the structure of these…

Group Theory · Mathematics 2021-01-27 Jonathan Fruchter

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