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Given a II$_1$ factor $M$, a W$^*$-subalgebra $Q\subset M$ is {\it compressible} if for any $\varepsilon>0$ there exists a finite set of unitary elements $\Cal U_0\subset \Cal U(M)$ such that $\| \frac{1}{|\Cal U_0|}\sum_{u\in \Cal U_0}…

Operator Algebras · Mathematics 2025-10-21 Sorin Popa

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

Jones and Penneys showed that a finite depth subfactor planar algebra embeds in the bipartite graph planar algebra of its principal graph, via a Markov towers of algebras approach. We relate several equivalent perspectives on the notion of…

Operator Algebras · Mathematics 2018-10-17 Desmond Coles , Peter Huston , David Penneys , Srivatsa Srinivas

Let $M$ be a factor with separable predual and $G$ a compact group of automorphisms of $M$ whose action is minimal, i.e. $M^{G^\prime}\cap M = C$, where $M^G$ denotes the $G$-fixed point subalgebra. Then every intemediate von Neumann…

funct-an · Mathematics 2008-02-03 Masaki Izumi , Roberto Longo , Sorin Popa

Let $\M$ be a type ${\rm II_1}$ factor and let $\tau$ be the faithful normal tracial state on $\M$. In this paper, we prove that given finite elements $X_1,\cdots X_n \in \M$, there is a finite decomposition of the identity into $N \in…

Operator Algebras · Mathematics 2023-03-21 Shilin Wen , Junsheng Fang , Zhaolin Yao

For a self-symmetric tracial von Neumann algebra $A$, we study rescalings of $A^{*n} * L\mathbb{F}_r$ for $n \in \mathbb{N}$ and $r \in (1, \infty]$ and use them to obtain an interpolation $\mathcal{F}_{s,r}(A)$ for all real numbers $s>0$…

Operator Algebras · Mathematics 2025-02-13 Ken Dykema , Junchen Zhao

We define Jones's planar algebra as a map of multicategories and constuct a planar algebra starting from a 1-cell in a pivotal strict 2-category. We prove finiteness results for the affine representations of finite depth planar algebras. We…

Quantum Algebra · Mathematics 2010-04-07 Shamindra Kumar Ghosh

We introduce a new iterative amalgamated free product construction of II$_1$ factors, and use it to construct a separable II$_1$ factor which does not have property Gamma and is not elementarily equivalent to the free group factor…

Operator Algebras · Mathematics 2023-06-01 Ionut Chifan , Adrian Ioana , Srivatsav Kunnawalkam Elayavalli

We prove several unique prime factorization results for tensor products of type II_1 factors coming from groups that can be realized either as subgroups of hyperbolic groups or as discrete subgroups of connected Lie groups of real rank 1.…

Operator Algebras · Mathematics 2009-11-10 Narutaka Ozawa , Sorin Popa

We provide a fairly large family of amalgamated free product groups $\Gamma=\Gamma_1\ast_{\Sigma}\Gamma_2$ whose amalgam structure can be completely recognized from their von Neumann algebras. Specifically, assume that $\Gamma_i$ is a…

Operator Algebras · Mathematics 2017-06-27 Ionut Chifan , Adrian Ioana

A II$_1$ factor $M$ has the {\it stable single generation} ({\it SSG}) property if any amplification $M^t$, $t>0$, can be generated as a von Neumann algebra by a single element. We discuss a conjecture stating that if $M$ is SSG, then $M$…

Operator Algebras · Mathematics 2020-06-18 Sorin Popa

We study the question how quickly products of a fixed conjugacy class in the projective unitary group of a II${}_1$-factor von Neumann algebra cover the entire group. Our result is that the number of factors that are needed is essentially…

Operator Algebras · Mathematics 2015-08-13 Philip A. Dowerk , Andreas Thom

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

We study the structure of the inverse limit of the graded algebras of local unitary invariant polynomials using its Hilbert series. For k subsystems, we conjecture that the inverse limit is a free algebra and the number of algebraically…

Quantum Physics · Physics 2015-05-27 Peter Vrana

For a finite $\mathbb{Z}$-algebra $R$, i.e., for a ring which is not necessarily associative or unitary, but whose additive group is finitely generated, we construct a decomposition of $R/{\rm Ann}(R)$ into directly indecomposable factors…

Rings and Algebras · Mathematics 2023-08-04 Martin Kreuzer , Alexei Miasnikov , Florian Walsh

We introduce the notion of a generalized Jung factor: a II$_1$ factor $M$ for which any two embeddings of $M$ into its ultrapower $M^{\mathcal U}$ are equivalent by an automorphism of $M^{\mathcal U}$. We show that $\mathcal R$ is not the…

Operator Algebras · Mathematics 2020-05-13 Scott Atkinson , Isaac Goldbring , Srivatsav Kunnawalkam Elayavalli

In this paper we use the description of free group factors as the von Neumann algebras of Berezin's deformation of the upper half-plane, modulo PSL$(2,{\Bbb Z})$. The derivative, in the deformation parameter, of the product in the…

Operator Algebras · Mathematics 2007-05-23 Florin G. Radulescu

We study a new class of infinite dimensional Lie algebras, which has important applications to the theory of integrable equations. The construction of these algebras is very similar to the one for automorphic functions and this motivates…

Mathematical Physics · Physics 2009-11-10 S. Lombardo , A. V. Mikhailov

We study factorization and dilation properties of Markov maps between von Neumann algebras equipped with normal faithful states, i.e., completely positive unital maps which preserve the given states and also intertwine their automorphism…

Operator Algebras · Mathematics 2015-05-19 Uffe Haagerup , Magdalena Musat

We give a characterization of extremal irreducible discrete subfactors $(N\subseteq M, E)$ where $N$ is type ${\rm II}_1$ in terms of connected W*-algebra objects in rigid C*-tensor categories. We prove an equivalence of categories where…

Operator Algebras · Mathematics 2018-01-09 Corey Jones , David Penneys