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We consider discrete random dynamical systems induced by a non-elementary group action on a non-proper hyperbolic space. We prove that if the system is ergodic and satisfies the ``asymptotic past and future independence condition'' as…

Dynamical Systems · Mathematics 2025-09-09 Corentin Le Bars

We describe the endomorphisms of the direct product of two free groups of finite rank and obtain conditions for which the subgroup of fixed points is finitely generated and we do the same for periodic points. We also describe the…

Group Theory · Mathematics 2022-06-29 André Carvalho

In this work, we are concerned with hierarchically hyperbolic spaces and hierarchically hyperbolic groups. Our main result is a wide generalization of a combination theorem of Behrstock, Hagen, and Sisto. In particular, as a consequence, we…

Group Theory · Mathematics 2019-09-25 Federico Berlai , Bruno Robbio

This paper is an introduction to the hyperbolic geometry of noncommutative polyballs B_n of bounded linear operators on Hilbert spaces. We use the theory of free pluriharmonic functions on polyballs and noncommutative Poisson kernels on…

Functional Analysis · Mathematics 2017-01-04 Gelu Popescu

This paper is devoted to the investigation of the property of order separability for HNN extensions and free products with commutative subgroups. Particularly it was proven that HNN extension of a free group with maximal connected cyclic…

Group Theory · Mathematics 2010-07-21 Vladimir V. Yedynak

We obtain a criterion for quasiconvexity of a subgroup of an amalgamated free product of two word hyperbolic groups along a virtually cyclic subgroup. The result provides a method of constructing new word hyperbolic group in class (Q), that…

Group Theory · Mathematics 2008-02-03 Ilya Kapovich

We give a complete criterion for when two hyperbolic automorphisms of a tree generate a free, discrete subgroup. The decision depends only on three geometric invariants: the translation lengths of the generators and the length of overlap of…

Group Theory · Mathematics 2025-12-02 Yukun Du , Sa'ar Hersonsky

In this paper we introduce a hyperbolic distance $\delta$ on the noncommutative open ball $[B(H)^n]_1$, where $B(H)$ is the algebra of all bounded linear operators on a Hilbert space $H$, which is a noncommutative extension of the…

Functional Analysis · Mathematics 2009-11-29 Gelu Popescu

We give examples of hyperbolic groups with finite-rank free subgroups of huge (Ackermannian) distortion.

Group Theory · Mathematics 2011-05-10 Noel Brady , Will Dison , Tim Riley

In this paper we study transitivity of partially hyperbolic endomorphisms of the two torus whose action in the first homology has two integer eigenvalues of moduli greater than one. We prove that if the Jacobian is everywhere greater than…

Dynamical Systems · Mathematics 2023-07-26 M. Andersson , W. Ranter

We introduce an obstruction to the existence of a coarse embedding of a given group or space into a hyperbolic group, or more generally into a hyperbolic graph of bounded degree. The condition we consider is "admitting exponentially many…

Group Theory · Mathematics 2017-10-19 David Hume , Alessandro Sisto

In this note we prove the claim given in the title. A group G is noncommutatively slender if each map from the fundamental group of the Hawaiian Earring to G factors through projection to a canonical free subgroup. Graham Higman, in his…

Group Theory · Mathematics 2019-08-13 Samuel M. Corson

Baker and Riley proved that a free group of rank 3 can be contained in a hyperbolic group as a subgroup for which the Cannon-Thurston map is not well-defined. By using their result, we show that the phenomenon occurs for not only a free…

Group Theory · Mathematics 2012-06-27 Yoshifumi Matsuda , Shin-ichi Oguni

Genevois recently classified which graph braid groups on $\ge 3$ strands are word hyperbolic. In the $3$-strand case, he asked whether all such word hyperbolic groups are actually free; this reduced to checking two infinite classes of…

Group Theory · Mathematics 2024-03-22 B. Appiah , P. Dani , W. Ge , C. Hudson , S. Jain , M. Lemoine , J. Murphy , J. Murray , A. Pandikkadan , K. Schreve , H. Vo

We show that the Gromov boundary of the free product of two infinite hyperbolic groups is uniquely determined up to homeomorphism by the homeomorphism types of the boundaries of its factors. We generalize this result to graphs of hyperbolic…

Group Theory · Mathematics 2013-03-28 A. Martin , J. Swiatkowski

We obtain a number of finiteness results for groups acting on Gromov-hyperbolic spaces. In particular we show that a torsion-free locally quasiconvex hyperbolic group has only finitely many conjugacy classes of $n$-generated one-ended…

Group Theory · Mathematics 2007-05-23 Ilya Kapovich , Richard Weidmann

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 study Dehn twists in the outer automorphism group of a finitely generated non-abelian free group. Our main result states that, under certain compatibility conditions, sufficiently large powers of finitely many Dehn twists generate a…

Group Theory · Mathematics 2026-02-25 Donggyun Seo

Building on the dictionary between Kleinian groups and rational maps, we establish new connections between the theories of hyperbolic groups and certain iterated maps, regarded as dynamical systems. In order to make the exposition…

Dynamical Systems · Mathematics 2010-11-02 Peter Haïssinsky , Kevin M. Pilgrim

We show that for any positive integer $n$ there exists a constant $C(n)>0$ such that any $n$-generated group $G$, which acts by isometries on a $\delta$-hyperbolic space (with $\delta>0$), is either free or has a nontrivial element with…

Group Theory · Mathematics 2007-05-23 Ilya Kapovich , Richard Weidmann