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We consider a class of proper actions of locally compact groups on imprimitivity bimodules over C*-algebras which behave like the proper actions on C*-algebras introduced by Rieffel in 1988. We prove that every such action gives rise to a…

Operator Algebras · Mathematics 2007-05-23 Astrid an Huef , Iain Raeburn , Dana P. Williams

Building on previous papers by Anantharaman-Delaroche (AD) we introduce and study the notion of AD-amenability for partial actions and Fell bundles over discrete groups. We prove that the cross-sectional C*-algebra of a Fell bundle is…

Operator Algebras · Mathematics 2021-08-12 Fernando Abadie , Alcides Buss , Damián Ferraro

We introduce and study actions of Fell bundles over discrete groups on Hilbert bundles. Many examples of such actions are presented. We discuss the connection with positive definite bundle maps between Fell bundles, culminating in the…

Operator Algebras · Mathematics 2026-04-14 Erik Bédos , Roberto Conti

In this work, we give a presentation of the prefix expansion Pr(G) of an inverse semigroup G as recently introduced by Lawson, Margolis and Steinberg which is similar to the universal inverse semigroup defined by the second named author in…

Operator Algebras · Mathematics 2013-12-11 Alcides Buss , Ruy Exel

We introduce a natural concept of positive definiteness for bundle maps between Fell bundles over (possibly different) discrete groups and describe several examples. Such maps induce completely positive maps between the associated full…

Operator Algebras · Mathematics 2025-07-03 Erik Bédos , Roberto Conti

The notion of a semitransitive binary action of a group $G$ on a topological space is introduced. A duality theorem is proved, establishing a bijective correspondence between semitransitive distributive binary $G$-spaces and topological…

General Topology · Mathematics 2026-05-05 Pavel S. Gevorgyan

We study the $C^*$-algebras associated to upper-semicontinuous Fell bundles over second-countable Hausdorff groupoids. Based on ideas going back to the Packer--Raeburn "Stabilization Trick," we construct from each such bundle a groupoid…

Operator Algebras · Mathematics 2016-05-23 Marius Ionescu , Alex Kumjian , Aidan Sims , Dana P. Williams

We investigate the representation theory of the crossed-product C*-algebra associated to a compact group G acting on a locally compact space X when the stability subgroups vary discontinuously. Our main result applies when G has a principal…

Operator Algebras · Mathematics 2015-08-27 Robert Archbold , Astrid an Huef

We study compatible actions (introduced by Brown and Loday in their work on the non-abelian tensor product of groups) in the category of Lie algebras over a fixed ring. We describe the Peiffer product via a new diagrammatic approach, which…

Rings and Algebras · Mathematics 2019-06-11 Davide di Micco

Given a C*-dynamical system (A,G,\alpha), we discuss conditions under which subalgebras of the multiplier algebra M(A) consisting of fixed points for \alpha are Morita-Rieffel equivalent to ideals in the crossed product of A by G. In case G…

Operator Algebras · Mathematics 2007-05-23 Ruy Exel

The recently developed theory of partial actions of discrete groups on $C^*$-algebras is extended. A related concept of actions of inverse semigroups on $C^*$-algebras is defined, including covariant representations and crossed products.…

funct-an · Mathematics 2008-02-03 Nandor Sieben

Let U, V, and W be multiplicative unitaries coming from discrete Kac systems such that W is an amenable normal submultiplicative unitary of V with quotient U. We define notions for right-Hilbert bimodules of coactions of S_V and (S_V)^,…

funct-an · Mathematics 2007-05-23 S. Kaliszewski , John Quigg

We show that the category A(G) of actions of a locally compact group G on C*-algebras (with equivariant nondegenerate *-homomorphisms into multiplier algebras) is equivalent, via a full-crossed-product functor, to a comma category of…

Operator Algebras · Mathematics 2007-11-14 S. Kaliszewski , John Quigg

Our goal in this paper and two sequels is to apply the Yamagami-Muhly-Williams equivalence theorem for Fell bundles over groupoids to recover and extend all known imprimitivity theorems involving groups. Here we extend Raeburn's symmetric…

Operator Algebras · Mathematics 2012-06-27 S. Kaliszewski , Paul S. Muhly , John Quigg , Dana P. Williams

We consider group actions of topological groups on C*-algebras of the types which occur in many physics models. These are singular actions in the sense that they need not be strongly continuous, or the group need not be locally compact. We…

Operator Algebras · Mathematics 2012-10-16 Hendrik Grundling , Karl-Hermann Neeb

With each Fell bundle over a discrete group G we associate a partial action of G on the spectrum of the unit fiber. We discuss the ideal structure of the corresponding full and reduced cross-sectional C*-algebras in terms of the dynamics of…

Operator Algebras · Mathematics 2015-04-23 Beatriz Abadie , Fernando Abadie

We present a number of findings concerning groupoid dynamical systems and groupoid crossed products. The primary result is an identification of the spectrum of the groupoid crossed product when the groupoid has continuously varying abelian…

Operator Algebras · Mathematics 2009-05-29 Geoff Goehle

Let B be a C*-algebra with a maximal coaction of a locally compact group G, and let N and H be closed normal subgroups of G with N contained in H. We show that the process Ind_(G/H)^G which uses Mansfield's bimodule to induce…

Operator Algebras · Mathematics 2007-05-23 Astrid an Huef , S. Kaliszewski , Iain Raeburn , Dana P. Williams

We consider a twisted action of a discrete group G on a unital C*-algebra A and give conditions ensuring that there is a bijective correspondence between the maximal invariant ideals of A and the maximal ideals in the associated reduced…

Operator Algebras · Mathematics 2023-07-19 Erik Bédos , Roberto Conti

In a recent paper the authors introduced universal and exotic generalized fixed-point algebras for weakly proper group actions on C*-algebras. Here we extend the notion of weakly proper actions to actions on Hilbert modules. As a result we…

Operator Algebras · Mathematics 2015-11-04 Alcides Buss , Siegfried Echterhoff