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We define and study fibrations of topological groupoids. We interpret a groupoid fibration L->H with fibre G as an action of H on G by groupoid equivalences. Our main result shows that a crossed product for an action of L is isomorphic to…

Operator Algebras · Mathematics 2016-04-08 Alcides Buss , Ralf Meyer

Given an inverse semigroup $S$ endowed with a partial action on a topological space $X$, we construct a groupoid of germs $S\ltimes X$ in a manner similar to Exel's groupoid of germs, and similarly a partial action of $S$ on an algebra $A$…

Rings and Algebras · Mathematics 2019-10-14 Luiz Gustavo Cordeiro , Viviane Beuter

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

We classify $\mathcal{R}$- and $\mathcal{L}$-cross-sections of partial wreath product of inverse semigroups. As a corollary, we get the description of $\mathcal{R}$- and $\mathcal{L}$-cross-sections of the semigroupof partial automorphisms…

Group Theory · Mathematics 2020-06-30 Eugenia Kochubinska

An inverse semigroup $S$ is a Howson inverse semigroup if the intersection of finitely generated inverse subsemigroups of $S$ is finitely generated. Given a locally finite action $\theta$ of a group $G$ on a semilattice $E$, it is proved…

Group Theory · Mathematics 2014-12-10 Pedro V. Silva , Filipa Soares

A Morita equivalence similar to that found by Green for crossed products by groups will be established for crossed products by inverse semigroups. More precisely, let $G$ be an inverse semigroup, $H$ a finite sub-inverse semigroup of $G$…

Operator Algebras · Mathematics 2017-07-13 Bernhard Burgstaller

We introduce a new notion of twisted actions of inverse semigroups and show that they correspond bijectively to certain regular Fell bundles over inverse semigroups, yielding in this way a structure classification of such bundles. These…

Operator Algebras · Mathematics 2014-02-26 Alcides Buss , Ruy Exel

In this paper we present the construction of explicit quasi-isomorphisms that compute the cyclic homology and periodic cyclic homology of crossed-product algebras associated with (discrete) group actions. In the first part we deal with…

K-Theory and Homology · Mathematics 2017-09-26 Raphael Ponge

This paper concerns a class of semigroups that arise as products $US$, associated to what we call `action pairs'. Here $U$ and $S$ are subsemigroups of a common monoid and, roughly speaking, $S$ has an action on the monoid completion $U^1$…

Rings and Algebras · Mathematics 2023-09-21 Scott Carson , Igor Dolinka , James East , Victoria Gould , Rida-e Zenab

We study the semicrossed product of a finite dimensional C^*-algebra by two types of commuting automorphisms, and identify them with matrix algebras of analytic functions in two variables. We look at the connections with semicrossed…

Operator Algebras · Mathematics 2007-05-23 Mohammed Ridha Alaimia , Justin R. Peters

In this work, we introduce the notion of a partial action of a group on a strict monoidal category. We propose, in the context of Monoidal categories, new constructions analogous to those existing for partial group actions over an algebra…

Category Theory · Mathematics 2024-12-18 Eliezer Batista , Felipe Lopes Castro , Mykola Khrypchenko

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 construct the crossed product of a C(X)-algebra by an endomorphism, in such a way that the endomorphism itself becomes induced by the bimodule of continuous sections of a vector bundle. Some motivating examples for such a construction…

Operator Algebras · Mathematics 2011-11-21 Ezio Vasselli

We develop a theory of crossed products by "actions" of Hecke pairs $(G, \Gamma)$, motivated by applications in non-abelian $C^*$-duality. Our approach gives back the usual crossed product construction whenever $G / \Gamma$ is a group and…

Operator Algebras · Mathematics 2012-12-27 Rui Palma

We consider a version of the notion of F-inverse semigroup (studied in the algebraic theory of inverse semigroups). We point out that an action of such an inverse semigroup on a locally compact space has associated a natural groupoid…

funct-an · Mathematics 2008-02-03 Alexandru Nica

Given a non-necessarily commutative unital ring $R$ and a unital partial representation $\Theta $ of a group $G$ into the Picard semigroup $\mathbf{PicS} (R)$ of the isomorphism classes of partially invertible $R$-bimodules, we construct an…

Rings and Algebras · Mathematics 2022-11-08 Mikhailo Dokuchaev , Itailma Rocha

We characterize supramenable groups in terms of existence of invariant probability measures for partial actions on compact Hausdorff spaces and existence of tracial states on partial crossed products. These characterizations show that, in…

Operator Algebras · Mathematics 2020-11-09 Eduardo P. Scarparo

We prove a structure result on proper extensions of two-sided restriction semigroups in terms of partial actions, generalizing respective results for monoids and for inverse semigroups and upgrading the latter. We introduce and study…

Rings and Algebras · Mathematics 2024-10-29 Mikhailo Dokuchaev , Mykola Khrypchenko , Ganna Kudryavtseva

One of pressing problems in mathematical physics is to find a generalized Poincar\'e symmetry that could be applied to nonflat space-times. As a step in this direction we define the semidirect product of groupoids $\Gamma_0 \rtimes…

Mathematical Physics · Physics 2011-07-12 Leszek Pysiak , Michał Eckstein , Michael Heller , Wiesław Sasin

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