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Let $G$ be a Hausdorff, \'etale groupoid that is minimal and topologically principal. We show that $C^*_r(G)$ is purely infinite simple if and only if all the nonzero positive elements of $C_0(G^0)$ are infinite in $C_r^*(G)$. If $G$ is a…

Operator Algebras · Mathematics 2014-08-13 Jonathan Brown , Lisa Orloff Clark , Adam Sierakowski

We address the classification problem for graph $C^*$-algebras of finite graphs (finitely many edges and vertices), containing the class of Cuntz-Krieger algebras as a prominent special case. Contrasting earlier work, we do not assume that…

Operator Algebras · Mathematics 2018-03-05 Søren Eilers , Gunnar Restorff , Efren Ruiz , Adam P. W. Sørensen

In this paper we describe a new method of defining C*-algebras from oriented combinatorial data, thereby generalizing the constructions of algebras from directed graphs, higher-rank graphs, and ordered groups. We show that only the most…

Operator Algebras · Mathematics 2014-05-21 Jack Spielberg

We show that an \'etale groupoid which is strongly amenable at infinity is amenable whenever its full and reduced $C^*$-algebras coincide.

Operator Algebras · Mathematics 2022-02-01 Julian Kranz

We show that if $G$ is a second countable locally compact Hausdorff \'etale groupoid carrying a suitable cocycle $c:G\to\mathbb{Z}$, then the reduced $C^*$-algebra of $G$ can be realised naturally as the Cuntz-Pimsner algebra of a…

Operator Algebras · Mathematics 2018-04-19 Adam Rennie , David Robertson , Aidan Sims

We give a one-to-one correspondence between ideals in the Steinberg algebra of a Hausdorff ample groupoid $G$, and certain families of ideals in the group algebras of isotropy groups in $G$. This generalises a known ideal correspondence…

Rings and Algebras · Mathematics 2021-09-20 Simon W. Rigby , Thibaud van den Hove

Given a graded ample, Hausdorff groupoid $G$, and an involutive field $K$, we consider the Steinberg algebra $A_K(G)$. We obtain necessary and sufficient conditions on $G$ under which the annihilator of any graded ideal of $A_K(G)$ is…

Rings and Algebras · Mathematics 2024-05-07 Morteza Ahmadi , Ahmad Moussavi

To a directed graph $E$ is associated a $C^*$-algebra $C^* (E)$ called a graph $C^*$-algebra. There is a canonical action $\gamma$ of ${\bf T}$ on $C^* (E)$, called the gauge action. In this paper we present necessary and sufficient…

Operator Algebras · Mathematics 2007-05-23 David Pask , Seung-Jai Rho

We consider a locally compact Hausdorff groupoid $G$ which is graded over a discrete group. Then the fibre over the identity is an open and closed subgroupoid $G_e$. We show that both the full and reduced C*-algebras of this subgroupoid…

Operator Algebras · Mathematics 2023-06-06 Becky Armstrong , Lisa Orloff Clark , Astrid an Huef

We prove that an isomorphism of graded Grothendieck groups $K^{gr}_0$ of two Leavitt path algebras induces an isomorphism of a certain quotient of algebraic filtered $K$-theory and consequently an isomorphism of filtered $K$-theory of their…

Rings and Algebras · Mathematics 2020-05-18 Pere Ara , Roozbeh Hazrat , Huanhuan Li

Given an ample, Hausdorff groupoid $\mathcal{G}$, and a unital commutative ring $R$, we consider the Steinberg algebra $A_R(\mathcal {G})$. First we prove a uniqueness theorem for this algebra and then, when $\mathcal{G}$ is graded by a…

Rings and Algebras · Mathematics 2016-09-12 Lisa Orloff Clark , Ruy Exel , Enrique Pardo

For an ample groupoid $\mathcal{G}$ and a unit $x$ of $\mathcal{G}$, Steinberg constructed the induction and restriction functors between the category of modules over the Steinberg algebra $A_R(\mathcal{G})$ and the category of modules over…

Rings and Algebras · Mathematics 2020-06-22 Quang Loc Nguyen , Bich Van Nguyen

Let E be a second-countable, locally compact, Hausdorff groupoid equipped with an action of T such that G:=E/T is a principal groupoid with Haar system \lambda. The twisted groupoid C*-algebra C*(E;G,\lambda) is a quotient of the C*-algebra…

Operator Algebras · Mathematics 2012-02-21 Lisa Orloff Clark , Astrid an Huef

We study two classes of inverse semigroups built from directed graphs, namely graph inverse semigroups and a new class of semigroups that we refer to as Leavitt inverse semigroups. These semigroups are closely related to graph…

Group Theory · Mathematics 2019-11-19 John Meakin , Zhengpan Wang

Given a normal subgroup bundle $\mathcal A$ of the isotropy bundle of a groupoid $\Sigma$, we obtain a twisted action of the quotient groupoid $\Sigma/\mathcal A$ on the bundle of group $C^*$-algebras determined by $\mathcal A$ whose…

Operator Algebras · Mathematics 2020-11-24 Marius Ionescu , Alex Kumjian , Jean N. Renault , Aidan Sims , Dana P. Williams

By a labeled graph $C^*$-algebra we mean a $C^*$-algebra associated to a labeled space $(E,\mathcal L,\mathcal E)$ consisting of a labeled graph $(E,\mathcal L)$ and the smallest normal accommodating set $\mathcal E$ of vertex subsets.…

Operator Algebras · Mathematics 2017-08-01 Ja A Jeong , Gi Hyun Park

We study the topological full group of ample groupoids over locally compact spaces. We extend Matui's definition of the topological full group from the compact, to the locally compact case. We provide two general classes of groupoids for…

Operator Algebras · Mathematics 2019-05-28 Petter Nyland , Eduard Ortega

We prove that the C*-algebra of a second-countable, \'etale, amenable groupoid is simple if and only if the groupoid is topologically principal and minimal. We also show that if G has totally disconnected unit space, then the associated…

Operator Algebras · Mathematics 2013-10-10 Jonathan H. Brown , Lisa Orloff Clark , Cynthia Farthing , Aidan Sims

Leavitt path algebras associate to directed graphs a $\mathbb Z$-graded algebra and in their simplest form recover the Leavitt algebras L(1,n). In this note, we introduce iterated Leavitt path algebras associated to directed weighted graphs…

Rings and Algebras · Mathematics 2010-05-12 R. Hazrat

The second author showed how Katsura's construction of the C*-algebra of a topological graph E may be twisted by a Hermitian line bundle L over the edge space E. The correspondence defining the algebra is obtained as the completion of the…

Operator Algebras · Mathematics 2017-01-25 Alex Kumjian , Hui Li
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