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Let $\Fth$ be a 2 graph generated by $m$ blue edges and $n$ red edges, and $\omega$ be the distinguished faithful state associated with its graph C*-algebra $\O_\theta$. In this paper, we characterize the factorness of the von Neumann…

Operator Algebras · Mathematics 2014-02-26 Dilian Yang

In this paper, we initiate the study of endomorphisms and modular theory of the graph C*-algebras $\O_{\theta}$of a 2-graph $\Fth$ on a single vertex. We prove that there is a semigroup isomorphism between unital endomorphisms of…

Operator Algebras · Mathematics 2009-10-10 Dilian Yang

We give a characterisation of factoriality of the groupoid von Neumann algebra $L(\mathcal{G})$ associated to a discrete measured groupoid $(\mathcal{G},\mu)$. We introduce the notion of groupoids with `infinite conjugacy classes' and show…

Operator Algebras · Mathematics 2024-12-10 Tey Berendschot , Soham Chakraborty , Milan Donvil , Se-Jin Kim

These notes provide an explanation of the type classification of von Neumann algebras, which has made many appearances in recent work on entanglement in quantum field theory and quantum gravity. The goal is to bridge a gap in the literature…

High Energy Physics - Theory · Physics 2025-09-30 Jonathan Sorce

Let M be a factor of type III with separable predual and with normal states phi_1,...,phi_k, omega with omega faithful. Let A be a finite dimensional C*-subalgebra of M. Then it is shown that there is a unitary operator u in M such that…

Operator Algebras · Mathematics 2014-02-26 Yasuyuki Kawahigashi , Yoshiko Ogata , Erling Størmer

Given a finite, directed, connected graph $\Gamma$ equipped with a weighting $\mu$ on its edges, we provide a construction of a von Neumann algebra equipped with a faithful, normal, positive linear functional…

Operator Algebras · Mathematics 2018-11-19 Michael Hartglass , Brent Nelson

In this short note, we construct an exotic example of a locally compact group $G$ with a Borel $2$-cocycle $\omega$ such that the non-twisted group von Neumann algebra $L(G)$ is a factor, while the twisted group von Neumann algebra…

Operator Algebras · Mathematics 2025-08-13 Stefaan Vaes

Starting from a (small) rigid C$^*$-tensor category $\mathscr{C}$ with simple unit, we construct von Neumann algebras associated to each of its objects. These algebras are factors and can be either semifinite (of type II$_1$ or II$_\infty$,…

Operator Algebras · Mathematics 2019-08-06 Luca Giorgetti , Wei Yuan

Let $A$ be a $C^*$-algebra. It is shown that every absolutely summing operator from $A$ into $\ell_2$ factors through a Hilbert space operator that belongs to the 4-Schatten- von Neumann class. We also provide finite dimensinal examples…

Functional Analysis · Mathematics 2016-09-07 Narcisse Randrianantoanina

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

We give some natural conditions on actions of discrete countable groups on abelian locally compact groups of Lie type that imply factoriality of the group von Neumann algebras of their semidirect products. This allows us to give a fairly…

Operator Algebras · Mathematics 2025-11-18 Soham Chakraborty , Chinmay Tamhankar

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

We study the von Neumann algebra generated by q--deformed Gaussian elements l_i+l_i^* where operators l_i fulfill the q--deformed canonical commutation relations l_i l_j^*-q l_j^* l_i=delta_{ij} for -1<q<1. We show that if the number of…

Operator Algebras · Mathematics 2009-11-10 Piotr Sniady

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

The groups distinguish their von Neumann algebras, in the case when these are factors.

Operator Algebras · Mathematics 2015-05-21 Sa Ge Lee

This paper includes a series of structural results for von Neumann algebras arising from measure preserving actions by product groups on probability spaces. Expanding upon the methods used earlier by the first two authors \cite{CS}, we…

Operator Algebras · Mathematics 2013-07-19 Ionut Chifan , Thomas Sinclair , Bogdan Udrea

We study several notions of ultraproducts of von Neumann algebras from a unifying viewpoint. In particular, we show that for a sigma-finite von Neumann algebra $M$, the ultraproduct $M^{\omega}$ introduced by Ocneanu is a corner of the…

Operator Algebras · Mathematics 2014-03-25 Hiroshi Ando , Uffe Haagerup

We investigate factoriality, Connes' type ${\rm III}$ invariants and fullness of arbitrary amalgamated free product von Neumann algebras using Popa's deformation/rigidity theory. Among other things, we generalize many previous structural…

Operator Algebras · Mathematics 2025-07-17 Cyril Houdayer , Yusuke Isono

We show that the left regular representation of Neretin groups is factorial, providing the first example of a non-discrete simple group with this property. This is based on a new criterion of factoriality for totally disconnected groups.…

Operator Algebras · Mathematics 2025-07-01 Basile Morando

We obtain a complete characterisation of factorial multiparameter Hecke von Neumann algebras associated with right-angled Coxeter groups. Considering their $\ell^p$-convolution algebra analogues, we exhibit an interesting parameter…

Operator Algebras · Mathematics 2023-02-28 Sven Raum , Adam Skalski
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