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Carrier graphs of groups representing subgroups of a given relatively hyperbolic groups are introduced and a combination theorem for relatively quasi-convex subgroups is proven. Subsequently a theory of folds for such carrier graphs is…

Group Theory · Mathematics 2026-04-10 Richard Weidmann , Thomas Weller

Let $V$ be a finite graph and let $\phi:V\rightarrow V$ be an irreducible train track map whose mapping torus has word-hyperbolic fundamental group $G$. Then $G$ acts freely and cocompactly on a CAT(0) cube complex.

Group Theory · Mathematics 2016-08-17 Mark F. Hagen , Daniel T. Wise

We study groups acting on CAT(0) square complexes. In particular we show if Y is a nonpositively curved (in the sense of A. D. Alexandrov) finite square complex and the vertex links of Y contain no simple loop consisting of five edges, then…

Group Theory · Mathematics 2007-05-23 Xiangdong Xie

We introduce the notions of geometric height and graded (geometric) relative hyperbolicity in this paper. We use these to characterize quasiconvexity in hyperbolic groups, relative quasiconvexity in relatively hyperbolic groups, and convex…

Geometric Topology · Mathematics 2020-07-20 Francois Dahmani , Mahan Mj

We construct several series of explicit presentations of infinite hyperbolic groups enjoying Kazhdan's property (T). Some of them are significantly shorter than the previously known shortest examples. Moreover, we show that some of those…

Group Theory · Mathematics 2021-01-05 Pierre-Emmanuel Caprace , Marston Conder , Marek Kaluba , Stefan Witzel

An interesting question about quasiconvexity in a hyperbolic group concerns finding classes of quasiconvex subsets that are closed under finite intersections. A known example is the class of all quasiconvex subgroups. However, not much is…

Group Theory · Mathematics 2007-05-23 Ashot Minasyan

Bowditch characterized relative hyperbolicity in terms of group actions on fine hyperbolic graphs with finitely many edge orbits and finite edge stabilizers. In this paper, we define generalized fine actions on hyperbolic graphs, in which…

Group Theory · Mathematics 2021-10-29 Eduard Einstein , Daniel Groves , Thomas Ng

Let $$1 \to H \to G \to Q \to 1$$ be an exact sequence where $H= \pi_1(S)$ is the fundamental group of a closed surface $S$ of genus greater than one, $G$ is hyperbolic and $Q$ is finitely generated free. The aim of this paper is to provide…

Geometric Topology · Mathematics 2024-11-20 Jason F. Manning , Mahan Mj , Michah Sageev

In this paper we study group actions on quasi-median graphs, or 'CAT(0) prism complexes', generalising the notion of CAT(0) cube complexes. We consider hyperplanes in a quasi-median graph $X$ and define the contact graph $\mathcal{C}X$ for…

Group Theory · Mathematics 2021-03-26 Motiejus Valiunas

We show that a one-ended simply connected at infinity hyperbolic group $G$ with enough codimension-1 surface subgroups has $\partial G \cong \mathbb{S}^2$. Combined with a result of Markovic, our result gives a new characterization of…

Group Theory · Mathematics 2018-03-16 Benjamin Beeker , Nir Lazarovich

In the context of CAT(0) cubical groups, we develop an analogue of the theory of curve complexes and subsurface projections. The role of the subsurfaces is played by a collection of convex subcomplexes called a \emph{factor system}, and the…

Geometric Topology · Mathematics 2017-06-14 Jason Behrstock , Mark F. Hagen , Alessandro Sisto

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 construct compact hyperbolic 3-manifolds with totally geodesic boundary, such that the closed 3-pseudomanifolds obtained by coning off the boundary components are negatively curved and contain locally convex subspaces whose fundamental…

Geometric Topology · Mathematics 2026-02-11 Jason Manning , Lorenzo Ruffoni

We construct a hyperbolic group with a finitely presented subgroup, which has infinitely many conjugacy classes of finite-order elements. We also use a version of Morse theory with high dimensional horizontal cells and use handle…

Group Theory · Mathematics 2009-05-04 Noel Brady , Matt Clay , Pallavi Dani

We study those groups that act properly discontinuously, cocompactly, and isometrically on CAT(0) spaces with isolated flats and the Relative Fellow Traveller Property. The groups in question include word hyperbolic CAT(0) groups as well as…

Metric Geometry · Mathematics 2008-03-18 G. Christopher Hruska

We show the mapping class group, CAT(0) groups, the fundamental groups of closed 3-manifolds, and certain relatively hyperbolic groups have a local-to-global property for Morse quasi-geodesics. This allows us to generalize combination…

Group Theory · Mathematics 2021-08-04 Jacob Russell , Davide Spriano , Hung Cong Tran

We consider a finitely generated virtually abelian group $G$ acting properly and without inversions on a CAT(0) cube complex $X$. We prove that $G$ stabilizes a finite dimensional CAT(0) subcomplex $Y \subseteq X$ that is isometrically…

Group Theory · Mathematics 2018-03-16 Daniel J. Woodhouse

We prove a combination theorem for hyperbolic groups, in the case of groups acting on complexes displaying combinatorial features reminiscent of non-positive curvature. Such complexes include for instance weakly systolic complexes and…

Group Theory · Mathematics 2019-09-19 Alexandre Martin , Damian Osajda

Many geometric structures associated to surface groups can be encoded in terms of invariant cross ratios on their circle at infinity; examples include points of Teichm\"uller space, Hitchin representations and geodesic currents. We add to…

Geometric Topology · Mathematics 2026-03-25 Jonas Beyrer , Elia Fioravanti

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