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We introduce a traceable operator-algebraic framework for incompressible transport on M= T3 (and, more generally, compact Riemannian manifolds endowed with a smooth invariant probability measure). Given an autonomous divergence-free…

Operator Algebras · Mathematics 2026-04-21 Gautier-Edouard Edouard Filardo

We obtain several rigidity results regarding tensor product decompositions of factors. First, we show that any full factor with separable predual has at most countably many tensor product decompositions up to stable unitary conjugacy. We…

Operator Algebras · Mathematics 2019-05-27 Yusuke Isono , Amine Marrakchi

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 define a new approximation property for tracial von Neumann algebras, called \textit{weakly mixing approximation property} which, for discrete groups and II$_1$ factors, is equivalent to the negation of Kazhdan's property (T).

Operator Algebras · Mathematics 2025-08-05 Paul Jolissaint

We give a description of operator algebras of free wreath products in terms of fundamental algebras of graphs of operator algebras as well as an explicit formula for the Haar state. This allows us to deduce stability properties for certain…

Operator Algebras · Mathematics 2024-02-22 Pierre Fima , Arthur Troupel

We say that a countable discrete group $\Gamma$ satisfies the invariant von Neumann subalgebras rigidity (ISR) property if every $\Gamma$- invariant von Neumann subalgebra $\mathcal{M}$ in $L(\Gamma)$ is of the form $L(\Lambda)$ for some…

Operator Algebras · Mathematics 2022-12-06 Tattwamasi Amrutam , Yongle Jiang

The notions of N=1 Neveu-Schwarz vertex operator superalgebra over a Grassmann algebra and with odd formal variables and of N=1 Neveu-Schwarz vertex operator superalgebra over a Grassmann algebra and without odd formal variables are…

Quantum Algebra · Mathematics 2007-05-23 Katrina Deane Barron

We prove an inverse theorem for the Gowers $U^2$-norm for maps $G\to\mathcal M$ from an countable, discrete, amenable group $G$ into a von Neumann algebra $\mathcal M$ equipped with an ultraweakly lower semi-continuous, unitarily invariant…

Operator Algebras · Mathematics 2019-02-20 Marcus De Chiffre , Narutaka Ozawa , Andreas Thom

This is a continuation of a previous joint work with Robert Weston on the quantum group invariant XXZ spin-chain (math-ph/0703085). The previous results on quasi-Hermiticity of this integrable model are briefly reviewed and then connected…

Mathematical Physics · Physics 2012-07-20 Christian Korff

Using a m\'elange of techniques at the rich intersection of deformation/rigidity theory, finite index subfactor theory, and geometric group theory, we prove the existence of a continuum of property (T) factors that are pairwise non-stably…

Operator Algebras · Mathematics 2025-11-11 Ionut Chifan , Junhwi Lim

Any Calderon-Zygmund operator T is pointwise dominated by a convergent sum of positive dyadic operators. We give an elementary self-contained proof of this fact, which is simpler than the probabilistic arguments used for all previous…

Classical Analysis and ODEs · Mathematics 2015-09-07 Tuomas P. Hytönen , Michael T. Lacey , Carlos Pérez

Recent work has highlighted the importance of crossed products in correctly elucidating the operator algebraic approach to quantum field theories. In the gravitational context, the crossed product simultaneously promotes von Neumann…

High Energy Physics - Theory · Physics 2024-06-28 Marc S. Klinger , Robert G. Leigh

We prove that if $G$ and $H$ are $\alpha$-back-and-forth equivalent groups (in the sense of computable structure theory) for some ordinal $\alpha \geq \omega$, then their group von Neumann algebras $L(G)$ and $L(H)$ are also…

Logic · Mathematics 2024-03-26 Isaac Goldbring , Matthew Harrison-Trainor

Recently, Adrian Ioana proved that all crossed products by free ergodic probability measure preserving actions of a nontrivial free product group \Gamma_1 * \Gamma_2 have a unique Cartan subalgebra up to unitary conjugacy. Ioana deduced…

Operator Algebras · Mathematics 2014-10-28 Stefaan Vaes

We introduce the operad Moor, dual of the operad NAP and the notion of Moor-bialgebras. We warn the reader that the compatibility relation linking the Moor-operation with the Moor-cooperation is not distributive in the sense of Loday.…

Quantum Algebra · Mathematics 2008-06-25 Leroux Philippe

Supramenability of groups is characterised in terms of invariant measures on locally compact spaces. This opens the door to constructing interesting crossed product C*-algebras for non-supramenable groups. In particular, stable Kirchberg…

Operator Algebras · Mathematics 2013-12-09 Julian Kellerhals , Nicolas Monod , Mikael Rordam

Applying Popa's orthogonality method to a new class of groups, we construct amenable group factors which are prime and have no infinite dimensional regular abelian *-subalgebras. By adjusting Farah--Katsura's solution of Dixmier's problem…

Operator Algebras · Mathematics 2021-03-02 Yuhei Suzuki

Recently, Hartz proved that every commuting contractive classical multishift with non-zero weights satisfies the matrix-version of von Neumann's inequality. We show that this result does not extend to the class of commuting operator-valued…

Functional Analysis · Mathematics 2018-11-07 Rajeev Gupta , Surjit Kumar , Shailesh Trivedi

In this paper, we give some properties of the fixed point algebra and the crossed product of a unital separable simple infinite dimensional C*-algebra by an action of a second-countable compact group with the tracial Rokhlin property with…

Operator Algebras · Mathematics 2025-07-08 Haotian Tian , Xiaochun Fang

We address two properties for Abelian topological groups: ``every closed subgroup is dually closed'' and ``every closed subgroup is dually embedded.'' We exhibit a pair of topological groups such that each has both of the properties and the…

General Topology · Mathematics 2007-05-23 Masasi Higasikawa
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