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Related papers: Relatively Hyperbolic Groups are $C^*$-simple

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We construct dense, unconditional subalgebras of the reduced group $C^*$-algebra of a word-hyperbolic group, which are closed under holomorphic functional calculus and possess many bounded traces. Applications to the cyclic cohomology of…

Operator Algebras · Mathematics 2009-04-24 Michael Puschnigg

We give a dynamical characterization of acylindrically hyperbolic groups. As an application, we prove that non-elementary convergence groups are acylindrically hyperbolic.

Group Theory · Mathematics 2019-08-21 Bin Sun

We define an algebraic group over a group $G$ to be a variety - that is, a subset of $G^d$ defined by equations over $G$ - endowed with a group law whose coordinates can be expressed as word maps. In the case where $G$ is a torsion-free…

Group Theory · Mathematics 2026-04-14 Vincent Guirardel , Chloé Perin

We show that if a group is not virtually cyclic and is hyperbolic relative to a family of proper subgroups, then it has a hyperbolically embedded subgroup which contains a finitely generated non-abelian free group as a finite index…

Group Theory · Mathematics 2012-05-23 Yoshifumi Matsuda , Shin-ichi Oguni , Saeko Yamagata

In this paper we create many examples of hyperbolic groups with subgroups satisfying interesting finiteness properties. We give the first examples of subgroups of hyperbolic groups which are of type $FP_2$ but not finitely presented. We…

Group Theory · Mathematics 2021-01-08 Robert Kropholler , Federico Vigolo

We classify the boundaries of hyperbolic groups that have enough quasiconvex codimension-1 surface subgroups with trivial or cyclic intersections.

Group Theory · Mathematics 2022-02-04 Benjamin Beeker , Nir Lazarovich

The aim of this short note is to provide a proof of the decidability of the generalized membership problem for relatively quasi-convex subgroups of finitely presented relatively hyperbolic groups, under some reasonably mild conditions on…

Group Theory · Mathematics 2020-05-27 Olga Kharlampovich , Pascal Weil

Let G be a group which is hyperbolic relative to a collection of subgroups A, and it is also hyperbolic relative to a collection of subgroups B. Suppose that the collection A contains B. We characterize, for subgroups of G, when…

Group Theory · Mathematics 2011-05-03 Eduardo Martinez-Pedroza

We study different notions of quasiconvexity for a subgroup $H$ of a relatively hyperbolic group $G.$ The first result establishes equivalent conditions for $H$ to be relatively quasiconvex. As a corollary we obtain that the relative…

Group Theory · Mathematics 2011-10-12 Victor Gerasimov , Leonid Potyagailo

We show that the $C^*$-algebra associated by Nekrashevych to a contracting self-similar group is simple if and only if the corresponding complex $\ast$-algebra is simple. We also improve on Steinberg and Szaka\'c's algorithm to determine if…

Operator Algebras · Mathematics 2025-01-22 Eusebio Gardella , Volodymyr Nekrashevych , Benjamin Steinberg , Alina Vdovina

Let $G$ be a group that is relatively hyperbolic with respect to a collection of subgroups $\{H_{\lambda}\}_{\lambda\in \Lambda}$. Suppose that $G$ is given by a finite relative presentation $\mathcal{P}$ with respect to this collection. We…

Group Theory · Mathematics 2025-01-09 Oleg Bogopolski

We show that a relatively hyperbolic group either is virtually cyclic or has uniform exponential growth.

Group Theory · Mathematics 2007-05-23 Xiangdong Xie

We give an example of a simple separable C*-algebra which is not isomorphic to its opposite algebra. Our example is nonnuclear and stably finite, has real rank zero and stable rank one, and has a unique tracial state. It has trivial K_1,…

Operator Algebras · Mathematics 2007-05-23 N. Christopher Phillips

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

We prove that a countable group with an effective minimal non-elementary convergence group action is a Powers group. More strongly we prove that it is a strongly Powers group and thus its non-trivial subnormal subgroups are $C^*$-simple.

Operator Algebras · Mathematics 2011-08-12 Yoshifumi Matsuda , Shin-ichi Oguni , Saeko Yamagata

We study the simplicity of $C^{*}$-algebras built from group actions. For a faithful isometric action of a group $G$ on a countable metric space $X$, we use the associated action representation on $\ell^2(X)$ to define the action-based…

Operator Algebras · Mathematics 2026-05-04 Tianyi Lou

It is shown that the reduced C*-algebra of a nontrivial linear group $\Gamma<GL_{d}(k)$ with trivial amenable radical is selfless. Thus selflessness and simplicity coincide for reduced C*-algebras of linear groups. Similar results are…

Operator Algebras · Mathematics 2026-02-16 Itamar Vigdorovich

Examples of simple, separable, unital, purely infinite $C^*$--algebras are constructed, including: (1) some that are not approximately divisible; (2) those that arise as crossed products of any of a certain class of $C^*$--algebras by any…

funct-an · Mathematics 2016-08-31 Kenneth J. Dykema , Mikael Rordam

We prove that a simple, separable, nuclear, purely infinite classifiable $C^*$-algebra is weakly semiprojective if and only if its $K$-groups are direct sums of cyclic groups.

Operator Algebras · Mathematics 2007-05-23 Jack Spielberg

We give a complete characterization of the locally compact groups that are non-elementary Gromov-hyperbolic and amenable. They coincide with the class of mapping tori of discrete or continuous one-parameter groups of compacting…

Group Theory · Mathematics 2015-10-29 Pierre-Emmanuel Caprace , Yves de Cornulier , Nicolas Monod , Romain Tessera