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In this paper we exhibit Morse geodesics, often called "hyperbolic directions", in infinite unbounded torsion groups. The groups studied are lacunary hyperbolic groups and constructed using graded small cancellation conditions. In all…

Group Theory · Mathematics 2017-11-01 Elisabeth Fink

We introduce and geometrically characterize the notion of uniformly perfect Morse boundary for proper geodesic metric spaces. As a unifying result, we prove that the Morse boundary of any finitely generated, non-elementary group is…

Group Theory · Mathematics 2026-02-09 Suzhen Han , Qing Liu

In this paper we study the generic, i.e., typical, behavior of finitely generated subgroups of hyperbolic groups and also the generic behavior of the word problem for amenable groups. We show that a random set of elements of a nonelementary…

Group Theory · Mathematics 2010-07-06 Robert Gilman , Alexei Miasnikov , Denis Osin

Given a finite graph of relatively hyperbolic groups with its fundamental group relatively hyperbolic and edge groups quasi-isometrically embedded and relatively quasiconvex in vertex groups, we prove that vertex groups are relatively…

Geometric Topology · Mathematics 2020-11-10 Abhijit Pal

In this paper, we study strongly quasiconvex subgroups in a finitely generated $3$--manifold group $\pi_1(M)$. We prove that if $M$ is a compact, orientable $3$--manifold that does not have a summand supporting the Sol geometry in its…

Group Theory · Mathematics 2020-07-07 Hoang Thanh Nguyen , Hung Cong Tran , Wenyuan Yang

We investigate the orbits of automaton semigroups and groups to obtain algorithmic and structural results, both for general automata but also for some special subclasses. First, we show that a more general version of the finiteness problem…

Formal Languages and Automata Theory · Computer Science 2020-07-21 Daniele D'Angeli , Dominik Francoeur , Emanuele Rodaro , Jan Philipp Wächter

For a fixed word hyperbolic group we compare different residual properties related to quasiconvex subgroups.

Group Theory · Mathematics 2007-05-23 Ashot Minasyan

Let S be a closed surface of genus at least 2. We show that a finitely generated group G which is an extension of the fundamental group H of S is word hyperbolic if and only the orbit map of the quotient group G/H on the complex of curves…

Geometric Topology · Mathematics 2015-05-06 Ursula Hamenstaedt

We prove a Morse Lemma for coarsely regular quasigeodesics in nonpositively curved symmetric spaces and euclidean buildings X. The main application is a simpler coarse geometric characterization of Morse subgroups of the isometry groups…

Group Theory · Mathematics 2018-12-19 Michael Kapovich , Bernhard Leeb , Joan Porti

In this paper we obtain uniform positive lower bounds on stable commutator length in word-hyperbolic groups and certain groups acting on hyperbolic spaces (namely the mapping class group acting on the complex of curves, and an amalgamated…

Group Theory · Mathematics 2009-12-06 Danny Calegari , Koji Fujiwara

In this paper, we present a notion of quasiconvexity in the setting of finitely-generated groups with hyperbolically embedded subgroups. Our main result shows that this notion yields uniform quasiconvex constants in the setting of coned-off…

Group Theory · Mathematics 2025-10-06 Ping Wan

We introduce the notion of graphical discreteness to group theory. A finitely generated group is graphically discrete if whenever it acts geometrically on a locally finite graph, the automorphism group of the graph is compact-by-discrete.…

Group Theory · Mathematics 2025-11-20 Alex Margolis , Sam Shepherd , Emily Stark , Daniel Woodhouse

We show that a finitely generated subgroup of the genus two handlebody group is stable if and only if the orbit map to the disk graph is a quasi-isometric embedding. To this end, we prove that the genus two handlebody group is a…

Geometric Topology · Mathematics 2023-04-06 Marissa Chesser

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 prove that, given a torsion-free relatively hyperbolic group G with non-relatively-hyperbolic peripherals, isomorphic finite index subgroups of G have the same index. This applies for instance to fundamental groups of finite-volume…

Group Theory · Mathematics 2025-09-05 Nir Lazarovich , Gon Rahamim , Alessandro Sisto

A subgroup H of a group G is called inert if for each $g\in G$ the index of $H\cap H^g$ in $H$ is finite. We give a classification of soluble-by-finite groups $G$ in which subnormal subgroups are inert in the cases where $G$ has no…

Group Theory · Mathematics 2015-04-10 Ulderico Dardano , Silvana Rinauro

The Morse local-to-global property generalizes the local-to-global property for quasi-geodesics in a hyperbolic space. We show that graph products of infinite Morse local-to-global groups have the Morse local-to-global property. To achieve…

Geometric Topology · Mathematics 2026-01-16 Joshua Perlmutter

We show that every virtually torsion-free subgroup of the outer automorphism group of a conjugacy separable relatively hyperbolic group is residually finite. As a direct consequence, we obtain that the outer automorphism group of a limit…

Group Theory · Mathematics 2009-07-29 V. Metaftsis , M. Sykiotis

We study automorphisms of a relatively hyperbolic group G. When G is one-ended, we describe Out(G) using a preferred JSJ tree over subgroups that are virtually cyclic or parabolic. In particular, when G is toral relatively hyperbolic,…

Group Theory · Mathematics 2014-03-06 Vincent Guirardel , Gilbert Levitt

We show that if $G$ is a non-elementary torsion-free word hyperbolic group then there exists another word hyperbolic group $G^*$, such that $G$ is a subgroup of $G^*$ but $G$ is not quasiconvex in $G^*$.

Group Theory · Mathematics 2009-09-25 Ilya Kapovich