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We establish rigidity theorems for graph product von Neumann algebras $M_\Gamma=*_{v,\Gamma}M_v$ associated to finite simple graphs $\Gamma$ and families of tracial von Neumann algebras $(M_v)_{v\in\Gamma}$. We consider the following three…

Operator Algebras · Mathematics 2025-09-09 Camille Horbez , Adrian Ioana

We compute the automorphism group of the intersection graph of many large-type Artin groups. This graph is an analogue of the curve graph of mapping class groups but in the context of Artin groups. As an application, we deduce a number of…

Group Theory · Mathematics 2024-07-30 Jingyin Huang , Damian Osajda , Nicolas Vaskou

Let $G$ be a right-angled Artin group with $|\mathrm{Out}(G)|<+\infty$. We prove that if a countable group $H$ with bounded torsion is measure equivalent to $G$, with an $L^1$-integrable measure equivalence cocycle towards $G$, then $H$ is…

Group Theory · Mathematics 2025-10-09 Camille Horbez , Jingyin Huang

We prove that if two transvection-free right-angled Artin groups are measure equivalent, then they have isomorphic extension graphs. As a consequence, two right-angled Artin groups with finite outer automorphism groups are measure…

Group Theory · Mathematics 2022-06-15 Camille Horbez , Jingyin Huang

We study $2$-dimensional Artin groups of hyperbolic type from the viewpoint of measure equivalence, and establish rigidity theorems. We first prove that they are boundary amenable. So is every group acting discretely by simplicial…

Group Theory · Mathematics 2021-10-11 Camille Horbez , Jingyin Huang

We prove that all (generalized) Higman groups on at least $5$ generators are superrigid for measure equivalence. More precisely, let $k\ge 5$, and let $H$ be a group with generators $a_1,\dots,a_k$, and Baumslag-Solitar relations given by…

Group Theory · Mathematics 2025-01-31 Camille Horbez , Jingyin Huang

In this paper we study the elementary theory of graph products of groups and show that under natural conditions on the vertex groups we can recover (the core of) the underlying graph and the associated vertex groups. More precisely, we…

Group Theory · Mathematics 2021-06-08 Montserrat Casals-Ruiz , Ilya Kazachkov , Javier de la Nuez González

We single out a large class of groups ${\mathscr{M}}$ for which the following unique prime factorization result holds: if $\Gamma_1,\dots,\Gamma_n\in {\mathscr{M}}$ and $\Gamma_1\times\dots\times\Gamma_n$ is measure equivalent to a product…

Operator Algebras · Mathematics 2022-09-28 Daniel Drimbe

We prove rigidity properties for von Neumann algebraic graph products. We introduce the notion of rigid graphs and define a class of II$_1$-factors named $\mathcal{C}_{\rm Rigid}$. For von Neumann algebras in this class we show a unique…

Operator Algebras · Mathematics 2026-05-13 Matthijs Borst , Martijn Caspers , Enli Chen

In this paper we study various rigidity aspects of the von Neumann algebra $L(\Gamma)$ where $\Gamma$ is a graph product group \cite{Gr90} whose underlying graph is a certain cycle of cliques and the vertex groups are the wreath-like…

Operator Algebras · Mathematics 2025-06-03 Ionut Chifan , Michael Davis , Daniel Drimbe

In \cite{CDD22} we investigated the structure of $\ast$-isomorphisms between von Neumann algebras $L(\Gamma)$ associated with graph product groups $\Gamma$ of flower-shaped graphs and property (T) wreath-like product vertex groups as in…

Operator Algebras · Mathematics 2025-06-03 Ionut Chifan , Michael Davis , Daniel Drimbe

A variant of Gromov's notion of measure equivalence for groups has been introduced for II$_1$ factors under different names. We propose the terminology of W*-correlated II$_1$ factors. We prove rigidity results up to W*-correlations for…

Operator Algebras · Mathematics 2025-08-13 Daniel Drimbe , Stefaan Vaes

We study relative bi-exactness of graph product and graph-wreath product group von Neumann algebras. In particular, we obtain the relative bi-exactness for graph product von Neumann algebras $LH_{\Gamma}=\ast_{v,\Gamma} LH_v$ and…

Operator Algebras · Mathematics 2026-01-27 Taisuke Hoshino

We establish new results and introduce new methods in the theory of measurable orbit equivalence, using bounded cohomology of group representations. Our rigidity statements hold for a wide (uncountable) class of groups arising from negative…

Group Theory · Mathematics 2007-05-23 Nicolas Monod , Yehuda Shalom

We study analytic properties of graph product of finite groups with a hyperbolic defining graph. This is done by studying dynamics on the Bowditch compactification of the extension graph, or the crossing graph, of graph product. In…

Group Theory · Mathematics 2024-12-25 Koichi Oyakawa

We get three types of results on measure equivalence rigidity; direct product groups of Ozawa's class $\mathcal{S}$ groups, wreath product groups and amalgamated free products. We prove measure equivalence factorization results on direct…

Group Theory · Mathematics 2014-08-07 Hiroki Sako

A {\it graph product} $G$ on a graph $\Gamma$ is a group defined as follows: For each vertex $v$ of $\Gamma$ there is a corresponding non-trivial group $G_v$. The group $G$ is the quotient of the free product of the $G_v$ by the commutation…

Group Theory · Mathematics 2020-04-24 Michael Mihalik

This article studies automorphism groups of graph products of arbitrary groups. We completely characterise automorphisms that preserve the set of conjugacy classes of vertex groups as those automorphisms that can be decomposed as a product…

Group Theory · Mathematics 2019-08-07 Anthony Genevois , Alexandre Martin

In the study of random structures we often face a trade-off between realism and tractability, the latter typically enabled by assuming some form of independence. In this work we initiate an effort to bridge this gap by developing tools that…

Discrete Mathematics · Computer Science 2015-03-02 Dimitris Achlioptas , Paris Siminelakis

We initiate a quantitative study of measure equivalence (and orbit equivalence) between finitely generated groups, which extends the classical setting of $\mathrm L^p$ measure equivalence. In this paper, our main focus will be on amenable…

Group Theory · Mathematics 2022-04-18 Thiebout Delabie , Juhani Koivisto , François Le Maître , Romain Tessera
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