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Let $\Phi:F\rightarrow F$ be an automorphism of the finite-rank free group $F$. Suppose that $G=F\rtimes_\Phi\mathbb Z$ is word-hyperbolic. Then $G$ acts freely and cocompactly on a CAT(0) cube complex.

Group Theory · Mathematics 2016-05-27 Mark F. Hagen , Daniel T. Wise

We refine Feighn--Handel's results on subgroups of mapping tori of free groups to the special case of free-by-cyclic groups. We use these refinements to show that any finitely generated free-by-cyclic group embeds in a {finitely generated…

Group Theory · Mathematics 2026-04-23 Marco Linton

We build quasi--isometry invariants of relatively hyperbolic groups which detect the hyperbolic parts of the group; these are variations of the stable dimension constructions previously introduced by the authors. We prove that, given any…

Group Theory · Mathematics 2016-09-19 Matthew Cordes , David Hume

In this paper we study residual solvability of the amalgamated product of two finitely generated free groups, in the case of doubles. We find conditions where this kind of structure is residually solvable, and show that in general this is…

Group Theory · Mathematics 2007-05-23 Delaram Kahrobaei

We construct nonlinear hyperbolic groups which are large, torsion-free, one-ended, and admit a finite $K(\pi,1)$. Our examples are built from superrigid cocompact rank one lattices via amalgamated free products and HNN extensions.

Group Theory · Mathematics 2019-04-24 Richard Canary , Matthew Stover , Konstantinos Tsouvalas

We show that all finitely generated free-by-cyclic groups are conjugacy separable: if a finitely generated group $G$ surjects onto $\mathbb{Z}$ with free kernel, then for every pair of non-conjugate elements $g,h\in G$, there exists a…

Group Theory · Mathematics 2026-04-22 François Dahmani , Sam Hughes , Monika Kudlinska , Nicholas Touikan

We provide sufficient conditions for two subgroups of a hierarchically hyperbolic group to generate an amalgamated free product over their intersection. The result applies in particular to certain geometric subgroups of mapping class groups…

Group Theory · Mathematics 2026-01-07 Giorgio Mangioni

We show that finitely generated mapping tori of free groups have a canonical collection of maximal sub-mapping tori of finitely generated free groups with respect to which they are relatively hyperbolic and locally relatively quasi-convex.…

Group Theory · Mathematics 2025-10-06 Marco Linton

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

In this paper we describe finitely generated groups $H$ universally equivalent (with constants from $G$ in the language) to a given torsion-free relatively hyperbolic group $G$ with free abelian parabolics. It turns out that, as in the free…

Group Theory · Mathematics 2013-05-17 O. Kharlampovich , A. Myasnikov

In this note, we prove that a random extension of either the free group $F_N$ of rank $N\ge3$ or of the fundamental group of a closed, orientable surface $S_g$ of genus $g\ge2$ is a hyperbolic group. Here, a random extension is one…

Geometric Topology · Mathematics 2015-01-14 Samuel J. Taylor , Giulio Tiozzo

It was conjectured in [KLS14] that non-elementary word hyperbolic groups are never invariably generated. We show that this is indeed the case even for the much larger class of convergence groups.

Group Theory · Mathematics 2014-12-03 Tsachik Gelander

We prove that for a finitely generated group G with a free factor system and an injective endomorphism that preserves the free factor system, the ascending HNN extension of G is hyperbolic relative to a collection of maximal parabolic…

Group Theory · Mathematics 2024-12-12 Swathi Krishna

We exhibit free-by-cyclic groups containing non-free locally-free subgroups, including some word hyperbolic examples. We also show that these groups are not subgroup separable. We use Bestvina-Brady Morse theory in our arguments.

Group Theory · Mathematics 2012-10-25 Ian J. Leary , Graham A. Niblo , Daniel T. Wise

A result of Baumslag and Roseblade states that a finitely presented subgroup of the direct product of two free groups is virtually a direct product of free groups. In this paper we generalise this result to the class of cyclic subgroup…

Group Theory · Mathematics 2023-10-03 Montserrat Casals-Ruiz , Jone Lopez de Gamiz Zearra

We consider the class of groups whose word problem is poly-context-free; that is, an intersection of finitely many context-free languages. We show that any group which is virtually a finitely generated subgroup of a direct product of free…

Group Theory · Mathematics 2015-10-09 Tara Brough

This arXived paper has two independant parts, that are improved and corrected versions of different parts of a single paper once named "On equations in relatively hyperbolic groups". The first part is entitled "Existential questions in…

Group Theory · Mathematics 2020-07-20 Francois Dahmani

Let $H$ be a torsion-free $\delta$-hyperbolic group with respect to a finite generating set $S$. Let $a_1,..., a_n$ and $a_{1*},..., a_{n*}$ be elements of $H$ such that $a_{i*}$ is conjugate to $a_i$ for each $i=1,..., n$. Then, there is a…

Group Theory · Mathematics 2010-02-24 O. Bogopolski , E. Ventura

We consider exponent equations in finitely generated groups. These are equations, where the variables appear as exponents of group elements and take values from the natural numbers. Solvability of such (systems of) equations has been…

Group Theory · Mathematics 2024-12-03 Michael Figelius , Markus Lohrey

Cyclic words are equivalence classes of cyclic permutations of ordinary words. When a group is given by a rewriting relation, a rewriting system on cyclic words is induced, which is used to construct algorithms to find minimal length…

Group Theory · Mathematics 2012-11-14 Volker Diekert , Andrew Duncan , Alexei Myasnikov