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Let $G$ be a discrete group acting on a von Neumann algebra $M$ by properly outer $*$-automorphisms. In this paper we study the containment $M \subseteq M\rtimes_\alpha G$ of $M$ inside the crossed product. We characterize the intermediate…

Operator Algebras · Mathematics 2016-09-09 Jan Cameron , Roger R. Smith

Suppose $N$ is a diffuse, property T von Neumann algebra and X is an arbitrary finite generating set of selfadjoint elements for N. By using rigidity/deformation arguments applied to representations of N in full matrix algebras, we deduce…

Operator Algebras · Mathematics 2007-05-23 Kenley Jung , Dimitri Shlyakhtenko

The purpose of this paper is to investigate the structure of Shlyakhtenko's free Araki-Woods factors using the framework of ultraproduct von Neumann algebras. We first prove that all the free Araki-Woods factors $\Gamma(H_{\mathbb R},…

Operator Algebras · Mathematics 2025-07-17 Cyril Houdayer , Sven Raum

In this article we consider partial abelianization of associative algebra with respect to a subalgebra. This notion is a generalization of usual abelianization of associative algebra and has an application in Quantum Mechanics and Quantum…

Representation Theory · Mathematics 2019-12-12 Anna Kocherova , Ilya Zhdanovskiy

Let $G$ be a finite group and let $N$ be a normal subgroup of $G$. We attach to $N$ two graphs ${\Gamma}_G(N)$ and ${\Gamma}^{\ast}_G(N)$ related to the conjugacy classes of $G$ contained in $N$ and to the set of primes dividing the sizes…

Group Theory · Mathematics 2024-02-12 Antonio Beltrán , María José Felipe , Carmen Melchor

A class of algebras is constructed using free fermions and the invariant antisymmetric tensors associated with irreducible holonomy groups. (This version contains minor typographical corrections and some additional references. )

High Energy Physics - Theory · Physics 2014-01-21 P. S. Howe , G. Papadopoulos , P. C. West

In 1957, N. G. de Bruijn showed that the symmetric group Sym(\Omega) on an infinite set \Omega contains a free subgroup on 2^{card(\Omega)} generators, and proved a more general statement, a sample consequence of which is that for any group…

Rings and Algebras · Mathematics 2021-10-15 George M. Bergman

We investigate free products of finite dimensional $C^*$-algebras with amalgamation over diagonal subalgebras. We look to determine under what circumstances a given free product is exact and/or nuclear. In some cases we find a description…

Operator Algebras · Mathematics 2013-07-23 Benton L. Duncan

A continuous family of non-outer conjugate aperiodic automorphisms whose crossed-products are all isomorphic is given on every interpolated free group factor. An explicit "duality" relationship between compact co-commutative Kac algebra…

Operator Algebras · Mathematics 2019-05-21 Fumio Hiai , Yoshimichi Ueda

We introduce the free inhomogeneous wreath product of compact matrix quantum groups, which generalizes the free wreath product (Bichon 2004). We use this to present a general technique to determine quantum automorphism groups of connected…

Quantum Algebra · Mathematics 2025-10-06 Josse van Dobben de Bruyn , Amaury Freslon , Prem Nigam Kar , David E. Roberson , Peter Zeman

In this paper, we consider the relation between the group freeness and the amalgamated freeness of crossed product algebras.

Operator Algebras · Mathematics 2007-05-23 Ilwoo Cho

We define a semidirect product groupoid of a system of partially defined local homeomorphisms $T=(T_{1},..., T_{r})$. We prove that this construction gives rise to amenable groupoids. The associated algebra is a Cuntz-like algebra. We use…

Operator Algebras · Mathematics 2008-11-12 Ionel Popescu , Iulian Popescu

We are able to explicitly compute the bimodule structure of von Neumann algebra inclusions in handle constructions, which arise as inductive limits of iterated amalgamated free products not elementarily equivalent to $L(\mathbb{F}_2)$. Our…

Operator Algebras · Mathematics 2026-02-03 David Gao , David Jekel , Srivatsav Kunnawalkam Elayavalli , Gregory Patchell

We show that any countably generated von Neumann algebra with specified normal faithful state can arise as the tail algebra of a quantum exchangeable sequence of noncommutative random variables. We also characterize the cases when the state…

Operator Algebras · Mathematics 2012-12-13 Kenneth J. Dykema , Claus Köstler

This is a brief review of our recent work attempted at a generalization of the Grassmann algebra to the paragrassmann ones. The main aim is constructing an algebraic basis for representing `fractional' symmetries appearing in $2D$…

High Energy Physics - Theory · Physics 2007-05-23 A. T. Filippov , A. B. Kurdikov

Let $M=M_1*M_2$ be a nontrivial tracial free product of finite von Neumann algebras. We prove that any amenable subalgebra of $M$ that has a diffuse intersection with $M_1$ is in fact contained in $M_1$. This has been proved by C. Houdayer…

Operator Algebras · Mathematics 2015-01-28 Narutaka Ozawa

In this paper we study free actions of groups on separated graphs and their \cstar{}algebras, generalizing previous results involving ordinary (directed) graphs. We prove a version of the Gross-Tucker Theorem for separated graphs yielding a…

Operator Algebras · Mathematics 2022-12-21 Pere Ara , Alcides Buss , Ado Dalla Costa

We study the two-sided Guionnet-Jones-Shlyakhtenko construction applied to the group planar algebra $P(\mathcal{G})$ of a finite non-trivial group $\mathcal{G}$. This produces a sequence of von Neumann algebras $M^k$ for $k \geq 0$ with no…

Operator Algebras · Mathematics 2025-10-02 R Jayakumar

In this paper, we consider the Wiener Hopf algebra, denoted $\mathcal{W}(A,P,G,\alpha)$, associated to an action of a discrete subsemigroup $P$ of a group $G$ on a $C^{*}$-algebra $A$. We show that $\mathcal{W}(A,P,G,\alpha)$ can be…

Operator Algebras · Mathematics 2015-10-06 S. Sundar

We consider absolutely free nonassociative algebras and, more generally, absolutely free algebras with (maybe infinitely) many multilinear operations. Such algebras are described in terms of labeled reduced planar rooted trees. This allows…

Rings and Algebras · Mathematics 2009-03-25 Vesselin Drensky , Ralf Holtkamp