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Given a partial action \alpha of a group G on an associative algebra A we consider the crossed product A x_\alpha G. Using the algebras of multipliers of ideals of A we prove that A x_\alpha G is associative, provided that all ideals of A…

Rings and Algebras · Mathematics 2010-03-16 M. Dokuchaev , R. Exel

The graph C*-algebra of a directed graph E is the universal C*-algebra generated by a family of partial isometries satisfying relations which reflect the path structure of E. In the first part of this paper we consider coverings of directed…

Operator Algebras · Mathematics 2007-05-23 Klaus Deicke , David Pask , Iain Raeburn

We show an isomorphism between the kernel of the C*-algebra of the tangent groupoid of a filtered manifold and the crossed product of the order 0 pseudodifferential operators in the associated filtered calculus by a natural R-action. This…

Operator Algebras · Mathematics 2025-04-08 Clément Cren

We consider a fixed free and proper action of a locally compact group $G$ on a space $T$, and actions $\alpha:G\to \Aut A$ on $C^*$-algebras for which there is an equivariant embedding of $(C_0(T),\rt)$ in $(M(A),\alpha)$. A recent theorem…

Operator Algebras · Mathematics 2009-07-06 Astrid an Huef , S. Kaliszewski , Iain Raeburn , Dana P. Williams

Every simply connected and connected solvable Lie group $G$ admits a simply transitive action on a nilpotent Lie group $H$ via affine transformations. Although the existence is guaranteed, not much is known about which Lie groups $G$ can…

Group Theory · Mathematics 2020-04-28 Jonas Deré , Marcos Origlia

Let $G \curvearrowright A$ be an action of a discrete group on a unital $C^*$-algebra by $*$-automorphisms. In this note, we give two sufficient dynamical conditions for the $C^*$-inclusion $A \subseteq A \rtimes_r G$ to be norming in the…

Operator Algebras · Mathematics 2023-07-31 David R. Pitts , Roger R. Smith , Vrej Zarikian

Suppose that $G$ is a groupoid acting on a small category $H$ in the sense of \cite[Definition 4]{NOT} and $H\times_\alpha G$ is the resulting semi-direct product category (as in \cite[Proposition 8]{NOT}). We show that there exists a…

Operator Algebras · Mathematics 2007-10-19 Han Li

Let A be an exact C^*-algebra, let G be a locally compact group, and let (A,G,\alpha) be a C*-dynamical system. Each automorphism \alpha_g induces a spatial automorphism Ad_{\lamba_g} on the reduced crossed product A\times_\alpha G. In this…

Operator Algebras · Mathematics 2007-05-23 Ciprian Pop , Roger R. Smith

We prove that the crossed product A x G of a separable, unital, quasidiagonal C*- algebra A by a discrete, countable, amenable, maximally almost periodic group G is quasidiagonal, provided that the action is almost periodic.

Operator Algebras · Mathematics 2013-01-22 Stefanos Orfanos

We study actions of locally compact groups on von Neumann factors and the associated crossed-product von Neumann algebras. In the setting of totally disconnected groups we provide sufficient conditions on an action $G\curvearrowright Q$…

Operator Algebras · Mathematics 2016-12-05 Rémi Boutonnet , Arnaud Brothier

We consider the crossed product $G_{ga}$ by $\R_+^*$ of the adiabatic groupoid associated with any Lie groupoid $G$. We construct an explicit Morita equivalence between the exact sequence of order 0 pseudodifferential operators on $G$ and…

Functional Analysis · Mathematics 2013-10-10 Claire Debord , Georges Skandalis

In this paper, we investigate the $H^p(G) \rightarrow L^p(G)$, $0< p \leq 1$, boundedness of multiplier operators defined via group Fourier transform on a graded Lie group $G$, where $H^p(G)$ is the Hardy space on $G$. Our main result…

Classical Analysis and ODEs · Mathematics 2022-10-07 Qing Hong , Guorong Hu , Michael Ruzhansky

We investigate approximation properties for $C^*$-algebras and their crossed products by actions and coactions by locally compact groups. We show that Haagerup's approximation constant is preserved for crossed products by arbitrary amenable…

Operator Algebras · Mathematics 2007-05-23 May Nilsen , Roger Smith

We introduce the tracial quasi-Rokhlin property for an automorphism alpha of a unital C*-algebra A, which is not assumed to be simple. We show that under suitable hypotheses, the associated crossed product C*-algebra C*(Z,A,alpha) is…

Operator Algebras · Mathematics 2013-07-01 Julian Buck

Let $p\in [1,\infty)$. We define an $L^p$-operator algebra crossed product by a transfer operator for the topological Bernoulli shift $\varphi$ on $X=\{1,...,n\}^{\mathbb{N}}$, and we prove it is isometrically isomorphic to the $L^p$-analog…

Functional Analysis · Mathematics 2023-10-27 Krzysztof Bardadyn

We introduce and study a new Banach algebra structure on the trace-zero subspace $\mathcal{T}(L^2(\mathbb{G}))_0$ of trace class operators for any locally compact quantum group $\mathbb{G}$; it is defined through a mixed Lie-type product of…

Operator Algebras · Mathematics 2026-02-24 Jason Crann , Matthias Neufang

We show that every operator on $L^{p}$, $1<p<\infty$ defined by multiplication by the identity function on $\mathbb{C}$ is a compact perturbation of an operator that is diagonal with respect to an unconditional basis. We also classify these…

Functional Analysis · Mathematics 2017-07-18 March Boedihardjo

Given a C*-dynamical system (A,G,\alpha), we say that A is a weakly proper (X\rtimes G)-algebra if there exists a proper G-space X together with a nondegenerate G-equivariant *-homomorphism \phi:C_0(X)->M(A). Weakly proper G-algebras form a…

Operator Algebras · Mathematics 2014-06-02 Alcides Buss , Siegfried Echterhoff

In this paper, we will prove that if $A$ is a $C^*$-algebra with an effective coaction $\epsilon$ by a compact quantum group, then the fixed point algebra and the reduced crossed product are Morita equivalent. As an application, we prove an…

funct-an · Mathematics 2008-02-03 Chi-Keung Ng

We prove that simple, separable, monotracial UHF $L^{p}$-operator algebras are not classifiable up to (complete) isomorphism using countable structures, such as K-theoretic data, as invariants. The same assertion holds even if one only…

Operator Algebras · Mathematics 2016-05-06 Eusebio Gardella , Martino Lupini