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We characterise the groupoid $C^*$-algebras associated to the transformation groupoids of injective actions of discrete countable Ore semi-groups on compact topological spaces in terms of the reduced crossed product from the dual actions,…

Operator Algebras · Mathematics 2024-04-23 Xiangqi Qiang , Chengjun Hou

We show that the Fra\"iss\'e limit of a category of unital separable $C^*$-algebras which is sufficiently closed under tensor products of its objects and morphisms is strongly self-absorbing, given that it has approximate inner half-flip.…

Operator Algebras · Mathematics 2021-03-03 Saeed Ghasemi

We study permanence properties of the classes of stable and so-called D-stable C*-algebras, respectively. More precisely, we show that a C_0(X)-algebra A is stable if all its fibres are, provided that the underlying compact metrizable space…

Operator Algebras · Mathematics 2007-05-23 Ilan Hirshberg , Mikael Rordam , Wilhelm Winter

We prove the first rigidity and classification theorems for crossed product von Neumann algebras given by actions of non-discrete, locally compact groups. We prove that for arbitrary free probability measure preserving actions of connected…

Operator Algebras · Mathematics 2018-07-20 Arnaud Brothier , Tobe Deprez , Stefaan Vaes

By combining R{\o}rdam's construction and the author's previous construction, we provide the first examples of amenable actions of non-amenable groups on simple separable nuclear C*-algebras that are neither stably finite nor purely…

Operator Algebras · Mathematics 2025-03-03 Yuhei Suzuki

Amenable actions of locally compact groups on von Neumann algebras are investigated by exploiting the natural module structure of the crossed product over the Fourier algebra of the acting group. The resulting characterisation of…

Operator Algebras · Mathematics 2021-01-20 Andrew McKee , Reyhaneh Pourshahami

Let $\mathfrak{C}$ be the smallest class of countable discrete groups with the following properties: (i) $\mathfrak{C}$ contains the trivial group, (ii) $\mathfrak{C}$ is closed under isomorphisms, countable increasing unions and extensions…

Operator Algebras · Mathematics 2024-11-19 Norio Nawata

A discrete group is said to be C*-simple if its reduced C*-algebra is simple, and is said to have the unique trace property if its reduced C*-algebra has a unique tracial state. A dynamical characterization of C*-simplicity was recently…

Operator Algebras · Mathematics 2017-12-14 Emmanuel Breuillard , Mehrdad Kalantar , Matthew Kennedy , Narutaka Ozawa

We provide a framework for studying concrete C*-algebras associated with algebraic actions of semigroups: Given such an action, we construct an inverse semigroup, and we introduce conditions for algebraic actions that characterize…

Operator Algebras · Mathematics 2024-01-25 Chris Bruce , Xin Li

Partial actions of discrete abelian groups can be used to construct both groupoid C*-algebras and partial crossed product algebras. In each case there is a natural notion of an analytic subalgebra. We show that for countable subgroups of…

Operator Algebras · Mathematics 2007-05-23 Allan P. Donsig , Alan Hopenwasser

We study the problem of determining when the reduced twisted group C*-algebra associated with a discrete group G is simple and/or has a unique tracial state, and present new sufficient conditions for this to hold. One of our main tools is a…

Operator Algebras · Mathematics 2017-06-06 Erik Bédos , Tron Omland

We show that separable, simple, unital C*-algebras with finite decomposition rank absorb the Jiang-Su algebra Z tensorially. This has a number of consequences for Elliott's program to classify nuclear C*-algebras by their K-theory data. In…

Operator Algebras · Mathematics 2009-08-28 Wilhelm Winter

Let $G$ be a countable discrete amenable group, ${\cal M}$ a McDuff factor von Neumann algebra, and $A$ a separable nuclear weakly dense C$^*$-subalgebra of ${\cal M}$. We show that if two centrally free actions of $G$ on ${\cal M}$ differ…

Operator Algebras · Mathematics 2011-04-22 Yasuhiko Sato

We study the C*-algebra crossed product $C_0(X)\rtimes G$ of a locally compact group $G$ acting properly on a locally compact Hausdorff space $X$. Under some mild extra conditions, which are automatic if $G$ is discrete or a Lie group, we…

K-Theory and Homology · Mathematics 2010-12-24 Heath Emerson , Siegfried Echterhoff

We study crossed products of arbitrary operator algebras by locally compact groups of completely isometric automorphisms. We develop an abstract theory that allows for generalizations of many of the fundamental results from the selfadjoint…

Operator Algebras · Mathematics 2018-11-21 Elias Katsoulis , Christopher Ramsey

We construct a simple, separable, unital, and nuclear C*-algebra with weakly unperforated K_0-group which does not absorb the Jiang-Su algebra Z tensorially. As a result, we obtain a stably finite counter-example to Elliott's classification…

Operator Algebras · Mathematics 2007-05-23 Andrew S. Toms

We consider the properties weak cancellation, K_1-surjectivity, good index theory, and K_1-injectivity for the class of extremally rich C*-algebras, and for the smaller class of isometrically rich C*-algebras. We establish all four…

Operator Algebras · Mathematics 2017-06-09 Lawrence G. Brown , Gert K. Pedersen

Consider an exact action of discrete group $G$ on a separable $C^*$-algebra $A$. It is shown that the reduced crossed product $A\rtimes_{\sigma, \lambda} G$ is strongly purely infinite - provided that the action of $G$ on any quotient $A/I$…

Operator Algebras · Mathematics 2016-08-03 Eberhard Kirchberg , Adam Sierakowski

This note provides some technical support to the proof of a result of W. Winter which shows that two unital separable simple amenable ${\cal Z}$-absorbing C*-algebras with locally finite decomposition property satisfying the UCT whose…

Operator Algebras · Mathematics 2008-03-05 Huaxin Lin

Let X be an infinite, compact, metrizable space of finite covering dimension and h a minimal homeomorphism of X. We prove that the crossed product of C(X) by h absorbs the Jiang-Su algebra tensorially and has finite nuclear dimension. As a…

Operator Algebras · Mathematics 2009-03-25 Andrew S. Toms , Wilhelm Winter
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