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von Neumann algebras have been playing an increasingly important role in the context of gauge theories and gravity. The crossed product presents a natural method for implementing constraints through the commutation theorem, rendering it a…

High Energy Physics - Theory · Physics 2025-02-10 Shadi Ali Ahmad , Marc S. Klinger , Simon Lin

For any pair $M,N$ of von Neumann algebras such that the algebraic tensor product $M\otimes N$ admits more than one $\mathrm{C}^*$-norm, the cardinal of the set of $\mathrm{C}^*$-norms is at least $ {2^{\aleph_0}}$. Moreover there is a…

Operator Algebras · Mathematics 2017-10-02 Narutaka Ozawa , Gilles Pisier

We consider the local deformation problem of coisotropic submanifolds inside Poisson manifolds. To this end the groupoid of coisotropic sections (with respect to some tubular neighbourhood) is introduced. Although the geometric content of…

Differential Geometry · Mathematics 2009-03-25 Florian Schaetz

For any injective von Neumann algebra R and any discrete, countable group G, which acts by *-automorphisms on R, we construct an idempotent mapping of an ultra-weakly dense subspace of B(H) onto the reducerd crossed product von Neumann…

Operator Algebras · Mathematics 2020-06-15 Erik Christensen

We study the relationship between the dynamics of the action $\alpha$ of a discrete group $G$ on a von Neumann algebra $M$, and structural properties of the associated crossed product inclusion $L(G) \subseteq M \rtimes_\alpha G$, and its…

Operator Algebras · Mathematics 2024-03-14 Jon Bannon , Jan Cameron , Ionut Chifan , Kunal Mukherjee , Roger Smith , Alan Wiggins

Let $G = G_{1} \times G_{2}$ be a product of two locally compact, second countable groups and $\mu \in \mathrm{Prob}(G)$ be of the form $\mu = \mu_{1} \times \mu_{2}$, where $\mu_{i} \in \mathrm{Prob}(G_{i})$. Let $(B,\nu_B)$ be the…

Operator Algebras · Mathematics 2025-08-27 Tattwamasi Amrutam , Yongle Jiang , Shuoxing Zhou

We prove a general criterion for a von Neumann algebra $M$ in order to be in standard form. It is formulated in terms of an everywhere defined, invertible, antilinear, a priori not necessarily bounded operator, intertwining $M$ with its…

Operator Algebras · Mathematics 2015-05-20 Francesco Fidaleo , László Zsidó

We study the ISR (von Neumann invariant subalgebra rigidity) property for certain discrete groups arising as semidirect products from algebraic actions on certain 2-torsion groups, mostly arising as direct products of $\mathbb{Z}_2$. We…

Operator Algebras · Mathematics 2025-07-29 Tattwamasi Amrutam , Artem Dudko , Yongle Jiang , Adam Skalski

Let $(\mathcal{G},\nu)$ be a $t$-discrete ergodic groupoid. Consider a finite Von Neumann algebra $\mathcal{M}$ with separable predual. We prove that every uniformly bounded measurable representation $\rho:\mathcal{G} \rightarrow…

Operator Algebras · Mathematics 2025-12-29 Alessio Savini

We completely classify the atomic summands in a graph product $(M,\varphi) = *_{v \in \mathcal{G}} (M_v,\varphi_v)$ of von Neumann algebras with faithful normal states. Each type I factor summand $(N,\psi)$ is a tensor product of type I…

Operator Algebras · Mathematics 2025-06-11 Ian Charlesworth , David Jekel

We study the von Neumann algebra, generated by the unitary representations of infinite-dimensional groups nilpotent group $B_0^{\mathbb N}$. The conditions of the irreducibility of the regular and quasiregular representations of…

Operator Algebras · Mathematics 2008-03-25 Alexandre Kosyak

We prove a variety of results about the group von Neumann algebras associated to Thompson-like groups arising from so called $d$-ary cloning systems. Cloning systems are a framework developed by Witzel and the second author, with a $d$-ary…

Operator Algebras · Mathematics 2022-01-11 Eli Bashwinger , Matthew C. B. Zaremsky

We study admissible transformations and Lie symmetries for a class of variable-coefficient Burgers equations. We combine the advanced methods of splitting into normalized subclasses and of mappings between classes that are generated by…

Mathematical Physics · Physics 2020-05-19 Stanislav Opanasenko , Alexander Bihlo , Roman O. Popovych

Mimicking the von Neumann version of Kustermans and Vaes' locally compact quantum groups, Franck Lesieur had introduced a notion of measured quantum groupoid, in the setting of von Neumann algebras. In this article, we suppose that the…

Operator Algebras · Mathematics 2009-11-24 Michel Enock

For a class of wreath-like product groups with property (T), we describe explicitly all the embeddings between their von Neumann algebras. This allows us to provide a continuum of ICC groups with property (T) whose von Neumann algebras are…

Operator Algebras · Mathematics 2025-11-12 Ionut Chifan , Adrian Ioana , Denis Osin , Bin Sun

The construction of an infinite tensor product of the C*-algebra C_0(R) is not obvious, because it is nonunital, and it has no nonzero projection. Based on a choice of an approximate identity, we construct here an infinite tensor product of…

Operator Algebras · Mathematics 2010-01-08 Hendrik Grundling , Karl-Hermann Neeb

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 show that when $M,N_{1},N_{2}$ are tracial von Neumann algebras with $M'\cap M^{\omega}$ abelian, $M'\cap(M\bar{\otimes}N_{1})^{\omega}$ and $M'\cap(M\bar{\otimes}N_{2})^{\omega}$ commute in…

Operator Algebras · Mathematics 2020-04-20 Yasuhito Hashiba

We study the category of left unital graded modules over the Steinberg algebra of a graded ample Hausdorff groupoid. In the first part of the paper, we show that this category is isomorphic to the category of unital left modules over the…

K-Theory and Homology · Mathematics 2018-04-04 Pere Ara , Roozbeh Hazrat , Huanhuan Li , Aidan Sims

One of pressing problems in mathematical physics is to find a generalized Poincar\'e symmetry that could be applied to nonflat space-times. As a step in this direction we define the semidirect product of groupoids $\Gamma_0 \rtimes…

Mathematical Physics · Physics 2011-07-12 Leszek Pysiak , Michał Eckstein , Michael Heller , Wiesław Sasin