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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

To a semisimple and cosemisimple Hopf algebra over an algebraically closed field, we associate a planar algebra defined by generators and relations and show that it is a connected, irreducible, spherical, non-degenerate planar algebra with…

Quantum Algebra · Mathematics 2007-05-23 Vijay Kodiyalam , V. S. Sunder

In this paper we are interested in examples of locally compact quantum groups $(M,\Delta)$ such that both von Neumann algebras, $M$ and the dual $\hat{M}$, are factors. There is a lot of known examples such that $(M,\hat{M})$ are…

Operator Algebras · Mathematics 2007-05-23 Pierre Fima

In this paper, we explicitly work out the subfactor planar algebra $P^{(N \subset Q)}$ for an intermediate subfactor $N \subset Q \subset M$ of an irreducible subfactor $N \subset M$ of finite index. We do this in terms of the subfactor…

Operator Algebras · Mathematics 2021-05-18 Keshab Chandra Bakshi

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 show that for any type ${\rm III_1}$ free Araki-Woods factor $\mathcal{M} = \Gamma(H_\R, U_t)"$ associated with an orthogonal representation $(U_t)$ of $\R$ on a separable real Hilbert space $H_\R$, the continuous core $M = \mathcal{M}…

Operator Algebras · Mathematics 2025-07-17 Cyril Houdayer

In 2005, Shen introduced a new invariant, $\mathcal G(N)$, of a diffuse von Neumann algebra $N$ with a fixed faithful trace, and he used this invariant to give a unified approach to showing that large classes of ${\mathrm{II}}_1$ factors…

Operator Algebras · Mathematics 2008-12-15 Ken Dykema , Allan Sinclair , Roger Smith , Stuart White

For every $n\in \mathbb{N}$ we obtain a separable II$_1$ factor $M$ and a maximally abelian subalgebra $A\subset M$ such that the space of maximally amenable extensions of $A$ in $M$ is affinely identified with the $n$ dimensional…

Operator Algebras · Mathematics 2024-10-16 Srivatsav Kunnawalkam Elayavalli , Gregory Patchell

Given a countable group G, we consider the sets S_factor(G), S_eqrel(G), of subgroups F of the positive real line for which there exists a free ergodic probability measure preserving action G on X such that the fundamental group of the…

Operator Algebras · Mathematics 2012-03-07 Sorin Popa , Stefaan Vaes

Let $G$ be a locally compact group, $L(G)$ be its group von Neumann algebra equipped with the Plancherel weight $\varphi_G$. In this paper, we consider the following two questions. (1) When is the restriction of $\varphi_G$ to the…

Operator Algebras · Mathematics 2025-09-19 Yuki Miyamoto

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

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

We characterize finite index depth 2 inclusions of type II_1 factors in terms of actions of weak Kac algebras and weak C*-Hopf algebras. If N\subset M \subset M_1 \subset M_2 \subset ... is the Jones tower constructed from such an inclusion…

Quantum Algebra · Mathematics 2007-05-23 D. Nikshych , L. Vainerman

We describe the subfactor planar algebra of an intermediate subfactor $N\subset Q \subset M$ of an extremal subfactor $N\subset M$ of finite Jones index which is not necessarily irreducible.

Operator Algebras · Mathematics 2022-03-23 Keshab Chandra Bakshi , Sruthymurali

We investigate a construction which associates a finite von Neumann algebra $M(\Gamma,\mu)$ to a finite weighted graph $(\Gamma,\mu)$. Pleasantly, but not surprisingly, the von Neumann algebra associated to to a `flower with $n$ petals' is…

Operator Algebras · Mathematics 2011-02-23 Madhushree Basu , Vijay Kodiyalam , V. S. Sunder

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

For $R_1,R_2,R_3,\dots$ a family of non isomorphic rings (or algebras) having each only 2 idempotents ($1$ and $0$), we classify up to isomorphism the rings (or algebras) obtained by taking products of powers of the different $R_i$. We show…

Rings and Algebras · Mathematics 2025-12-24 Mohamad Maassarani

We develop an analog of Jones' planar calculus for II_1-factor bimodules with arbitrary left and right von Neumann dimension. We generalize to bimodules Burns' results on rotations and extremality for infinite index subfactors. These…

Operator Algebras · Mathematics 2015-05-30 David Penneys

Given a von Neumann algebra $M$ equipped with a faithful normal strictly semifinite weight $\varphi$, we develop a notion of Murray-von Neumann dimension over $(M,\varphi)$ that is defined for modules over the basic construction associated…

Operator Algebras · Mathematics 2025-03-25 Aldo Garcia Guinto , Matthew Lorentz , Brent Nelson

We use continuous model theory to obtain several results concerning isomorphisms and embeddings between II_1 factors and their ultrapowers. Among other things, we show that for any II_1 factor M, there are continuum many nonisomorphic…

Operator Algebras · Mathematics 2017-05-17 Ilijas Farah , Bradd Hart , David Sherman