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We study the C*-algebra crossed-product of the closed unit disk by the action of one of its conformal automorphisms. After classifying the conformal automorphisms up to topological conjugacy, we investigate, for each class, the irreducible…

Operator Algebras · Mathematics 2011-10-10 Man-Duen Choi , Frederic Latremoliere

We characterize the compact multiplication operators on a semi-crossed product in terms of the corresponding dynamical system. We also characterize the compact elements of this algebra and determine the ideal they generate.

Operator Algebras · Mathematics 2021-10-18 G. Andreolas , M. Anoussis , C. Magiatis

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

It is well-known that the maximalization of a coaction of a locally compact group on a C*-algebra enjoys a universal property. We show how this important property can be deduced from a categorical framework by exploiting certain properties…

Operator Algebras · Mathematics 2023-08-17 Erik Bédos , S. Kaliszewski , John Quigg , Jonathan Turk

We give complete descriptions of the tracial states on both the universal and reduced crossed products of a C*-dynamical system consisting of a unital C*-algebra and a discrete group. In particular, we also answer the question of when the…

Operator Algebras · Mathematics 2021-08-19 Dan Ursu

We examine the semicrossed products of a semigroup action by $*$-endomorphisms on a C*-algebra, or more generally of an action on an arbitrary operator algebra by completely contractive endomorphisms. The choice of allowable representations…

Operator Algebras · Mathematics 2018-08-17 Kenneth R. Davidson , Adam H. Fuller , Evgenios T. A. Kakariadis

We describe the structure of the irreducible representations of crossed products of unital C*-algebras by actions of finite groups in terms of irreducible representations of the C*-algebras on which the groups act. We then apply this…

Operator Algebras · Mathematics 2011-10-10 Alvaro Arias , Frederic Latremoliere

We define spectral freeness for actions of discrete groups on C*-algebras. We relate spectral freeness to other freeness conditions; an example result is that for an action of a finite group, spectral freeness is equivalent to strong…

Operator Algebras · Mathematics 2013-08-23 Cornel Pasnicu , N. Christopher Phillips

I combine recent results in the structure theory of nuclear C*-algebras and in topological dynamics to classify certain types of crossed products in terms of their Elliott invariants. In particular, transformation group C*-algebras…

Operator Algebras · Mathematics 2015-04-08 Wilhelm Winter

The purpose of this paper is to introduce a consistent notion of universal and reduced crossed products by actions and coactions of groups on operator systems and operator spaces. In particular we shall put emphasis to reveal the full power…

Operator Algebras · Mathematics 2019-10-16 Massoud Amini , Siegfried Echterhoff , Hamed Nikpey

In this paper, we give some properties of the fixed point algebra and the crossed product of a unital separable simple infinite dimensional C*-algebra by an action of a second-countable compact group with the tracial Rokhlin property with…

Operator Algebras · Mathematics 2025-07-08 Haotian Tian , Xiaochun Fang

Let $\mathcal{C}$ be a C*-algebra and $\alpha:\mathcal{C} \rightarrow \mathcal{C}$ a unital *-endomorphism. There is a natural way to construct operator algebras which are called semicrossed products, using a convolution induced by the…

Operator Algebras · Mathematics 2018-08-17 Evgenios T. A. Kakariadis

We give a description of traces on C(X)\rtimes G in terms of measurable fields of traces on the C*-algebras of the stabilizers of the action of G on X.

Operator Algebras · Mathematics 2010-10-05 Sergey Neshveyev

In this work we present a new definition to the Partial Crossed Product by actions of inverse semigroups in a C^*-algebra, without using the covariant representations as Sieben did in [5]. Also we present an isomorphism between the partial…

Operator Algebras · Mathematics 2008-05-26 Ruy Exel , Felipe Vieira

We define the decomposition property for partial actions of discrete groups on $C^*$-algebras. Decomposable partial systems appear naturally in practice, and many commonly occurring partial actions can be decomposed into partial actions…

Operator Algebras · Mathematics 2022-01-25 Fernando Abadie , Eusebio Gardella , Shirly Geffen

We consider reduced crossed products of twisted C*-dynamical systems over C*-simple groups. We prove there is a bijective correspondence between maximal ideals of the reduced crossed product and maximal invariant ideals of the underlying…

Operator Algebras · Mathematics 2016-02-05 Rasmus Sylvester Bryder , Matthew Kennedy

We show that for a closed embedding $\mathbb{H}\le \mathbb{G}$ of locally compact quantum groups (LCQGs) with $\mathbb{G}/\mathbb{H}$ admitting an invariant probability measure, a unitary $\mathbb{G}$-representation is type-I if its…

Operator Algebras · Mathematics 2022-03-01 Alexandru Chirvasitu

Let $G$ be a second countable, locally compact groupoid with Haar system, and let $\mathcal{A}$ be a bundle of $C^{\ast}$-algebras defined over the unit space of $G$ on which $G$ acts continuously. We determine conditions under which the…

Operator Algebras · Mathematics 2007-05-23 Igor Fulman , Paul S. Muhly , Dana P. Williams

Starting from an arbitrary endomorphism \alpha of a unital C*-algebra A we construct a crossed product. It is shown that the natural construction depends not only on the C*-dynamical system (A,\alpha) but also on the choice of an ideal…

Operator Algebras · Mathematics 2014-12-31 B. K. Kwasniewski , A. V. Lebedev

Suppose that $G$ has a representation group $H$, that $G_{ab}:= G/\bar{[G,G]}$ is compactly generated, and that $A$ is a \cs-algebra for which the complete regularization of $\Prim(A)$ is a locally compact Hausdorff space $X$. In a previous…

funct-an · Mathematics 2008-02-03 Siegfried Echterhoff , Dana P. Williams