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For a von Neumann algebra $\cal M$ with a faithful normal tracial state $\tau$ and a positive ergodic homomorphism $\alpha:\mathcal L^1(\mathcal M,\tau)\to \mathcal L^1(\mathcal M,\tau)$ such that $\alpha$ does not increase the norm in…

Operator Algebras · Mathematics 2014-05-20 Semyon Litvinov

Voiculescu's notion of asymptotic free independence applies to a wide range of random matrices, including those that are independent and unitarily invariant. In this work, we generalize this notion by considering random matrices with a…

Operator Algebras · Mathematics 2025-04-03 Ion Nechita , Sang-Jun Park

Using free probability constructions involving Cuntz-Pimsner C*-algebras we show that the topological entropy of the free product of two automorphisms is equal to the maximum of the individual entropies. As applications we show that general…

Operator Algebras · Mathematics 2007-05-23 N. P. Brown , K. Dykema , D. Shlyakhtenko

Let $G$ be a countable abelian group. We construct a unital simple projectionless C*-algebra $A$ with a unique tracial state, that satisfies $(K_0(A), [1_A]) \cong (\Z, 1) $, $K_1(A) \cong G$, absorbs the Jiang-Su algebra tensorially, and…

Operator Algebras · Mathematics 2009-03-31 Yasuhiko Sato

Let Gamma be a semidirect product of the form Z^n rtimes Z/p where p is prime and the Z/p-action on Z^n is free away from the origin. We will compute the topological K-theory of the real and complex group C*-algebra of Gamma and show that…

K-Theory and Homology · Mathematics 2015-11-30 James F. Davis , Wolfgang Lueck

We explore the dynamics of graph maps with zero topological entropy. It is shown that a continuous map $f$ on a topological graph $G$ has zero topological entropy if and only if it is locally mean equicontinuous, that is the dynamics on…

Dynamical Systems · Mathematics 2017-11-10 Jian Li , Piotr Oprocha , Yini Yang , Tiaoying Zeng

We study the class of selfless C*-probability spaces introduced by Robert. It is known that a selfless tracial algebra has strict comparison and a unique trace. We prove that for separable tracial C*-algebras, selflessness is equivalent to…

Operator Algebras · Mathematics 2026-04-29 Ali Jabbari

Within the framework of free actions of compact quantum groups on unital C*-algebras, we propose two conjectures. The first one states that, if $H$ is the C*-algebra of a compact quantum group coacting freely on a unital C*-algebra $A$,…

Quantum Algebra · Mathematics 2016-11-16 Paul F. Baum , Ludwik Dabrowski , Piotr M. Hajac

In this paper, we study the non-degenerated $C$-pseudo-cones which can be uniquely decomposed into the sum of a $C$-asymptotic set and a $C$-starting point. Combining this with the novel work in…

Metric Geometry · Mathematics 2024-11-12 Xudong Wang , Wenxue Xu , Jiazu Zhou , Baocheng Zhu

Let A_E be the canonical AF subalgebra of a graph C*-algebra C*(E) associated with a locally finite directed graph E. For Brown-Voiculescu's topological entropy ht(\Phi_E) of the canonical completely positive map \Phi_E on C*(E),…

Operator Algebras · Mathematics 2007-05-23 Ja A Jeong , Gi Hyun Park

In this short note we prove that every maximal torus action on the free algebra is conjugate to a linear action. This statement is the free algebra analogue of a classical theorem of A. Bia{\l}ynicki-Birula.

Algebraic Geometry · Mathematics 2020-08-31 Andrey Elishev , Alexei Kanel-Belov , Farrokh Razavinia , Jie-Tai Yu , Wenchao Zhang

We examine the problem of the linearity of an algebraic torus action in the associative setting. We prove the free algebra analog of a classical theorem of BialynickiBirula, which establishes linearity of maximal torus action. Additionally,…

Algebraic Geometry · Mathematics 2025-03-13 Alexei Belov-Kanel , Andrey Elishev , Farrokh Razavinia , Louis Rowen , Jie-Tai Yu , Wenchao Zhang

We show that, if A is a separable simple unital C*-algebra which absorbs the Jiang-Su algebra Z tensorially and which has real rank zero and finite decomposition rank, then A is tracially AF in the sense of Lin, without any restriction on…

Operator Algebras · Mathematics 2007-05-23 Wilhelm Winter

We show that the problem of classifying, up to isomorphism, the collection of zero-entropy mixing automorphisms of a standard non-atomic probability space, is intractible. More precisely, the collection of isomorphic pairs of automorphisms…

Dynamical Systems · Mathematics 2025-09-12 Marlies Gerber , Philipp Kunde

Let A be a C*-algebra with real rank zero which has the stable weak cancellation property. Let I be an ideal of A such that I is stable and satisfies the corona factorization property. We prove that 0->I->A->A/I->0 is a full extension if…

Operator Algebras · Mathematics 2021-09-20 Søren Eilers , Gunnar Restorff , Efren Ruiz

We provide an operator algebraic proof of a classical theorem of Thoma which characterizes the extremal characters of the infinite symmetric group $\mathbb{S}_\infty$. Our methods are based on noncommutative conditional independence…

Operator Algebras · Mathematics 2010-06-01 Rolf Gohm , Claus Köstler

We study selflessness in the general setting of reduced free products of $C^*$-algebras. Towards this end, we develop a suitable theory of rapid decay for filtrations in arbitrary $C^*$-probability spaces. We provide several natural…

Operator Algebras · Mathematics 2025-06-17 Ben Hayes , Srivatsav Kunnawalkam Elayavalli , Leonel Robert

We introduce certain $C^*$-algebras and $k$-graphs associated to $k$ finite dimensional unitary representations $\rho_1,...,\rho_k$ of a compact group $G$. We define a higher rank Doplicher-Roberts algebra $\mathcal{O}_{\rho_1,...,\rho_k}$,…

Operator Algebras · Mathematics 2020-06-26 Valentin Deaconu

We analyze the algebra of observables of a charged particle on a noncommutative torus in a constant magnetic field. We present a set of generators of this algebra which coincide with the generators for a commutative torus but at a different…

High Energy Physics - Theory · Physics 2009-11-07 Bogdan Morariu , Alexios P. Polychronakos

Motivated by a question of L. Robert, asking whether $\rm L(T(A)) = Lsc_{C}(T(A))$ for any separable C*-algebra A, we introduce and initiate the study of \emph{tracially reflexive C*-algebras}. We first prove that commutative C*-algebras…

Operator Algebras · Mathematics 2026-05-22 Laurent Cantier