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We formally introduce the concept of localizing the Elliott conjecture at a given strongly self-absorbing C*-algebra $D$; we also explain how the known classification theorems for nuclear C*-algebras fit into this concept. As a new result…

Operator Algebras · Mathematics 2007-09-12 Wilhelm Winter

We study the groupoid C*-algebras associated to the equivalence relation induced by a quotient map on a locally compact Hausdorff space. This C*-algebra is always a Fell algebra, and if the quotient space is Hausdorff, it is a…

Operator Algebras · Mathematics 2012-07-12 Lisa Orloff Clark , Astrid an Huef , Iain Raeburn

Let G be second countable locally compact Hausdorff groupoid with a continuous Haar system. We remove the assumption of amenability in a theorem of Clark about groupoids whose $C^*$-algebras are CCR. We show that if the groupoid C*-algebra…

Operator Algebras · Mathematics 2018-07-25 Daniel W van Wyk

We characterize when the reduced C*-algebra of a group has unique tracial state, respectively, is simple, in terms of Dixmier-type properties of the group C*-algebra. We also give a simple proof of the recent result by Breuillard, Kalantar,…

Operator Algebras · Mathematics 2016-06-14 Uffe Haagerup

The construction of the C*-algebra associated to a directed graph $E$ is extended to incorporate a family $C$ consisting of partitions of the sets of edges emanating from the vertices of $E$. These C*-algebras $C^*(E,C)$ are analyzed in…

Operator Algebras · Mathematics 2011-07-12 P. Ara , K. R. Goodearl

We consider groups G which have a cocompact, 3-manifold model for the classifying space \underline{E}G. We provide an algorithm for computing the rationalized equivariant K-homology of \underline{E}G. Under the additional hypothesis that…

K-Theory and Homology · Mathematics 2013-04-30 Jean-François Lafont , Ivonne J. Ortiz , Rubén J. Sánchez-García

We give an example of a simple separable C*-algebra which is not isomorphic to its opposite algebra. Our example is nonnuclear and stably finite, has real rank zero and stable rank one, and has a unique tracial state. It has trivial K_1,…

Operator Algebras · Mathematics 2007-05-23 N. Christopher Phillips

We show, based on previous results, that two separable simple stably projectionless amenable ${\cal Z}$-stable $C^*$-algebras which satisfy the UCT are isomorphic if and only if they have the same Elliott invariant.

Operator Algebras · Mathematics 2021-12-30 Guihua Gong , Huaxin Lin

We give an alternative construction of the essential $C^*$-algebra of an \'etale groupoid, along with an ``amenability'' notion for such groupoids that is implied by the nuclearity of this essential $C^*$-algebra. In order to do this we…

Operator Algebras · Mathematics 2025-04-18 Alcides Buss , Diego Martínez

We construct an uncountable family of pairwise nonisomorphic AH algebras with the same Elliott invariant and same radius of comparison. They can be distinguished by a local radius of comparison function, naturally defined on the positive…

Operator Algebras · Mathematics 2024-07-04 Ilan Hirshberg , N. Christopher Phillips

In the 1970s Alain Connes identified the appropriate notion of amenabilty for von Neumann algebras, and used it to obtain a deep internal finite dimensional approximation structure for these algebras. This structure is exactly what is…

Operator Algebras · Mathematics 2023-07-11 Stuart White

We examine two classes of examples of Hausdorff \'etale factor groupoids; one comes from taking a quotient space of the unit space of an AF-groupoid, and the other comes from certain nonhomogeneous extensions of Cantor minimal systems…

Operator Algebras · Mathematics 2023-05-02 Mitch Haslehurst

Let $C^*$-algebra that is acted upon by a compact abelian group. We show that if the fixed-point algebra of the action contains a Cartan subalgebra $D$ satisfying an appropriate regularity condition, then $A$ is the reduced $C^*$-algebra of…

Operator Algebras · Mathematics 2019-09-12 Jonathan Brown , Adam Fuller , David Pitts , Sarah Reznikoff

The main aim of this paper is to prove $R$-triviality for simple, simply connected algebraic groups with Tits index $E_{8,2}^{78}$ or $E_{7,1}^{78}$, defined over a field $k$ of arbitrary characteristic. Let $G$ be such a group. We prove…

Group Theory · Mathematics 2017-04-26 Maneesh Thakur

Let a compact group G act on real or complex C*-algebras A and B, with A separable and B sigma-unital. We express the G-equivariant Kasparov groups KK_n(A,B) by algebraic K-groups of a certain additive category.

K-Theory and Homology · Mathematics 2007-05-23 Tamaz Kandelaki

Suppose $G$ is a second countable, locally compact, Hausdorff groupoid with a fixed left Haar system. Let $\go/G$ denote the orbit space of $G$ and $\cs(G)$ denote the groupoid $C^*$-algebra. Suppose that $G$ is a principal groupoid. We…

Operator Algebras · Mathematics 2007-05-23 Lisa Orloff Clark

It is now well known that a simple graph $C^*$-algebra $C^*(E)$ of a directed graph $E$ is either AF or purely infinite. In this paper, we address the question of whether this is the case for labeled graph $C^*$-algebras recently introduced…

Operator Algebras · Mathematics 2016-03-01 Ja A Jeong , Eun Ji Kang , Sun Ho Kim , Gi Hyun Park

The Jiang--Su algebra Z has come to prominence in the classification program for nuclear C*-algebras of late, due primarily to the fact that Elliott's classification conjecture predicts that all simple, separable, and nuclear C*-algebras…

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

Let $C$ and $A$ be two unital separable amenable simple C*-algebras with tracial rank no more than one. Suppose that $C$ satisfies the Universal Coefficient Theorem and suppose that $\phi_1, \phi_2: C\to A$ are two unital monomorphisms. We…

Operator Algebras · Mathematics 2009-01-13 Huaxin Lin

It is proved that the K_0-group of a cluster C*-algebra is isomorphic to the corresponding cluster algebra. As a corollary, one gets a shorter proof of the positivity conjecture for cluster algebras. As an example, we consider a cluster…

Operator Algebras · Mathematics 2020-09-07 Igor Nikolaev