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We introduce a new invariant \mathcal{S}(M) for type III factors M with no almost-periodic weights. We compute this invariant for certain free Araki-Woods factors. We show that Connes' invariant \tau cannot distinguish all isomorphism…

Operator Algebras · Mathematics 2007-05-23 Dimitri Shlyakhtenko

Type III_1 factors arising as (direct summands of) von Neumann algebraic free products are investigated. In particular we compute Connes' Sd- and tau- invariants for those type III_1 factors without any extra assumption.

Operator Algebras · Mathematics 2019-05-21 Yoshimichi Ueda

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 tensor product $M \mathbin{\overline{\otimes}} N$ of any two full factors $M$ and $N$ (possibly of type ${\rm III}$) is full and we compute Connes' invariant $\tau(M \mathbin{\overline{\otimes}} N)$ in terms of $\tau(M)$…

Operator Algebras · Mathematics 2025-07-17 Cyril Houdayer , Amine Marrakchi , Peter Verraedt

We prove rigidity and classification results for type III factors given by nonsingular Bernoulli actions of the free groups and more general free product groups. This includes a large family of nonisomorphic Bernoulli crossed products of…

Operator Algebras · Mathematics 2023-07-11 Stefaan Vaes , Bram Verjans

In this article we introduce an isomorphism invariant for type II_1 factors using the Connes-Folner condition. We compute bounds of this number for free group factors.

Operator Algebras · Mathematics 2007-05-23 Jon P. Bannon , Mohan Ravichandran

In \cite{Ioana:vNsuperrigidity}, Ioana introduced three new invariants of type II$_1$ factors: the one-sided fundamental group, the endomorphism semigroup and the set of right-finite bimodules. In \cite{Ioana:vNsuperrigidity}, he does not…

Operator Algebras · Mathematics 2013-01-15 Steven Deprez

For each $\lambda\in\left]0,1\right]$ we exhibit an uncountable family of compact quantum groups $\mathbb{G}$ such that the von Neumann algebra $\mathsf{L}^{\!\infty}(\mathbb{G})$ is the injective factor of type $\mathrm{III}_\lambda$ with…

Operator Algebras · Mathematics 2024-09-05 Jacek Krajczok , Piotr M. Sołtan

We prove that it is not possible to classify separable von Neumann factors of types $\II_1$, $\II_\infty$ or $\III_\lambda$, $0\leq \lambda\leq1$, up to isomorphism by a Borel measurable assignment of "countable structures" as invariants.…

Operator Algebras · Mathematics 2009-03-27 Roman Sasyk , Asger Tornquist

We investigate the structure of crossed product von Neumann algebras arising from Bogoljubov actions of countable groups on Shlyakhtenko's free Araki-Woods factors. Among other results, we settle the questions of factoriality and Connes'…

Operator Algebras · Mathematics 2025-07-17 Cyril Houdayer , Benjamin Trom

We prove that, for any type III$_1$ free product factor, its continuous core is full if and only if its $\tau$-invariant is the usual topology on the real line. This trivially implies, as a particular case, the same result for free…

Operator Algebras · Mathematics 2019-05-21 Reiji Tomatsu , Yoshimichi Ueda

In the first part of the paper we survey several results from Popa's deformation/rigidity theory on the classification of tensor product decompositions of large natural classes of II$_1$ factors. Using a m\'elange of techniques from…

Operator Algebras · Mathematics 2022-08-02 Ionut Chifan , Daniel Drimbe , Adrian Ioana

We give a spectral gap characterization of fullness for type $\mathrm{III}$ factors which is the analog of a theorem of Connes in the tracial case. Using this criterion, we generalize a theorem of Jones by proving that if $M$ is a full…

Operator Algebras · Mathematics 2016-11-16 Amine Marrakchi

We prove that if C is a tensor C*-category in a certain class, then there exists an uncountable family of pairwise non stably isomorphic II_1 factors (M_i) such that the bimodule category of M_i is equivalent to C for all i. In particular,…

Operator Algebras · Mathematics 2013-03-07 Sébastien Falguières , Sven Raum

Crossed products with noncommutative Bernoulli actions were introduced by Connes as the first examples of full factors of type III. This article provides a complete classification of the factors $(P,\phi)^{\mathbb{F}_n} \rtimes…

Operator Algebras · Mathematics 2015-05-22 Stefaan Vaes , Peter Verraedt

We construct a class of II_1 factors M that admit unclassifiably many Cartan subalgebras in the sense that the equivalence relation of being conjugate by an automorphism of M is complete analytic, in particular non Borel. We also construct…

Operator Algebras · Mathematics 2012-08-20 An Speelman , Stefaan Vaes

We prove that there exist uncountably many separable II$_1$ factors whose ultrapowers (with respect to arbitrary ultrafilters) are non-isomorphic. In fact, we prove that the families of non-isomorphic II$_1$ factors originally introduced by…

Operator Algebras · Mathematics 2017-10-18 Rémi Boutonnet , Ionut Chifan , Adrian Ioana

For any given integer $n\geq 1$, we construct i.c.c. groups $G$ such that the II$_1$ factors $L(G)$ have exactly $n$-many $G$-invariant von Neumann subalgebras not arising from subgroups.

Operator Algebras · Mathematics 2026-05-05 Yongle Jiang , Qinxuan Xu

Using a family of graded algebra structures on a planar algebra and a family of traces coming from random matrix theory, we obtain a tower of non-commutative probability spaces, naturally associated to a given planar algebra. The associated…

Operator Algebras · Mathematics 2008-07-08 A. Guionnet , V. F. R. Jones , D. Shlyakhtenko

In this paper, we generalize Izumi's result on uniqueness of realization of finite C$^*$-tensor categories in the endomorphism category of the injective factor of type II_1 for finitely generated strongly amenable C$^*$-tensor categories by…

Operator Algebras · Mathematics 2016-11-03 Toshihiko Masuda
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