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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

A twisted ring is a ring endowed with a family of endomorphisms satisfying certain relations. One may then consider the notions of twisted module and twisted differential module. We study them and show that, under some general hypothesis,…

Algebraic Geometry · Mathematics 2015-03-18 Bernard Le Stum , Adolfo Quirós

We define the notion of a partial action on a generalized Boolean algebra and associate to every such system and commutative unital ring $R$ an $R$-algebra. We prove that every strongly $E^{\ast}$-unitary inverse semigroup has an associated…

Rings and Algebras · Mathematics 2025-03-04 Allen Zhang

We develop a structural theory of chirality for inverse semigroups and show how it propagates canonically to \'{e}tale groupoids and twisted groupoid $C^*$-algebras. Starting from inverse semigroup data equipped with admissible twist…

Operator Algebras · Mathematics 2026-02-27 Takao Inoué

Morita equivalence of twisted inverse semigroup actions and discrete twisted partial actions are introduced. Morita equivalent actions have Morita equivalent crossed products.

Operator Algebras · Mathematics 2010-10-05 Nandor Sieben

Categorical bundles provide a natural framework for gauge theories involving multiple gauge groups. Unlike the case of traditional bundles there are distinct notions of triviality, and hence also of local triviality, for categorical…

Differential Geometry · Mathematics 2015-12-09 Saikat Chatterjee , Amitabha Lahiri , Ambar N. Sengupta

This is a book about Partial Actions and Fell Bundles with applications to C*-algebras generated by partial isometries. Here is the table of contents: 1-Introduction, 2-Partial actions, 3-Restriction and globalization, 4-Inverse semigroups,…

Operator Algebras · Mathematics 2017-08-30 Ruy Exel

Let G be a group and let P be a subsemigroup of G. In order to describe the crossed product of a C*-algebra A by an action of P by unital endomorphisms we find that we must extend the action to the whole group G. This extension fits into a…

Operator Algebras · Mathematics 2010-03-16 Ruy Exel

J. Renault has recently found a generalization of the caracterization of C*-diagonals obtained by A. Kumjian in the eighties, which in turn is a C*-algebraic version of J. Feldman and C. Moore's well known Theorem on Cartan subalgebras of…

Operator Algebras · Mathematics 2008-06-26 Ruy Exel

We classify dynamical twists in group algebras of finite groups. Namely, we set up a bijective correspondence between gauge equivalence classes of dynamical twists (which are solutions of a certain non-linear functional equation) and…

Quantum Algebra · Mathematics 2007-05-23 Pavel Etingof , Dmitri Nikshych

We prove a version of Wordingham's theorem for left regular representations in the setting of Fell bundles of inverse semigroups and use this result to discuss the various associated cross sectional C*-algebras.

Operator Algebras · Mathematics 2016-11-11 Erik Bédos , Magnus D. Norling

We introduce notions of weak and strong equivalence for non-saturated Fell bundles over locally compact groups and show that every Fell bundle is strongly (resp. weakly) equivalent to a semidirect product Fell bundle for a partial (resp.…

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

We study the exactness of the reduced crossed product of a semigroup dynamical system and the reduced $C^{*}$-algebra of a product system. We show that for a semigroup dynamical system $(A, P,\alpha)$, under reasonable hypotheses (e.g., $P$…

Operator Algebras · Mathematics 2026-04-07 Md Amir Hossain , S. Sundar

We will show the raitonality of some twisted symmetric group actions.

Algebraic Geometry · Mathematics 2009-09-25 Akinari Hoshi , Ming-chang Kang

We introduce {\it covariant structures} $\left\{(\A,\k),(\a,\aa),\(\ha,\haa\)\right\}$ formed of a separable $C^*$-algebra $\A$, a measurable twisted action $(\a,\aa)$ of the second-countable locally compact group $\G$\,, a measurable…

Operator Algebras · Mathematics 2014-06-30 H. Bustos , M. Mantoiu

We show that there is an action of the symmetric group on the Hochschild cochain complex of a twisted group algebra with coefficients in a bimodule. This allows us to define the symmetric Hochschild cohomology of twisted group algebras,…

K-Theory and Homology · Mathematics 2021-03-26 Tiberiu Coconet , Constantin-Cosmin Todea

We study the notion of $1$-twisted semi-homogeneous vector bundles on $\mathbb{G}_m$-gerbes over abelian varieties, and classify point objects in the twisted derived categories of abelian varieties. As an application, we classify the…

Algebraic Geometry · Mathematics 2026-03-25 Ruoxi Li

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 extend the notion of T-duality to manifolds endowed with non-principal torus actions. The singularities of the torus action are controlled by a certain Lie algebroid, called the elliptic tangent bundle. Using this Lie algebroid, we…

Differential Geometry · Mathematics 2025-03-25 Gil R. Cavalcanti , Aldo Witte

The classical notion of twisted product is studied in the context of partial actions, in particular, we show that the globalization of a partial action is a twisted product. In addition, we establish conditions for the metrizability of…

General Topology · Mathematics 2024-01-04 Luis Martínez , Héctor Pinedo
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