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Families of codes such as group codes, constacyclic and skew cyclic codes, some of which independently suggested in the literature, turn out to be special instances of the general family of crossed product codes. Hamming-metric is a main…

Rings and Algebras · Mathematics 2018-11-06 Yuval Ginosar , Aviram Rochas Moreno

We extend the theory of Fourier--Stieltjes algebras to the category of twisted actions by \'etale groupoids on arbitrary C*-bundles, generalizing theories constructed previously by B\'{e}dos and Conti for twisted group actions on unital…

Operator Algebras · Mathematics 2025-11-18 Alcides Buss , Bartosz Kwaśniewski , Andrew McKee , Adam Skalski

We introduce the class of partially invertible modules and show that it is an inverse category which we call the Picard inverse category. We use this category to generalize the classical construction of crossed products to, what we call,…

Rings and Algebras · Mathematics 2018-12-14 Patrik Nystedt , Johan Öinert , Héctor Pinedo

We define $\mathcal{H}$-fibration sequences as fibrations where the holonomy action of the fundamental group of the base on the fiber lies in a given subgroup $\mathcal{H}$ of $\mathcal{E}(F)$, where $\mathcal{E}(F)$ is the homotopy…

Algebraic Topology · Mathematics 2021-05-12 Mario Fuentes

In this paper we suggest a definition for a C*-algebra attached to an injective morphism of some \'Etale groupoid. We take into account all the peculiarities of such objects and present some interesting relations with already well-known…

Operator Algebras · Mathematics 2022-04-22 Bruno Tadeu Costa , Renan Gambale Romano , Felipe Vieira

Given a fibration in groupoids d : D -> I, we define a fibered multicategory as a particular functor p : M -> I, where M has the same objects as D, and its arrows a : X -> Y should be thought of as families of arrows in the multicategory,…

Category Theory · Mathematics 2022-01-07 Claudio Pisani

Partial actions of discrete abelian groups can be used to construct both groupoid C*-algebras and partial crossed product algebras. In each case there is a natural notion of an analytic subalgebra. We show that for countable subgroups of…

Operator Algebras · Mathematics 2007-05-23 Allan P. Donsig , Alan Hopenwasser

For an action $\alpha$ of a locally compact group $G$ on a dual operator space $X$ by w*-continuous completely isometric isomorphisms one can define two generally different notions of crossed products, namely the Fubini crossed product…

Operator Algebras · Mathematics 2019-10-02 Dimitrios Andreou

Given a category fibered in groupoids over schemes with a log structure, one produces a category fibered in groupoids over log schemes. We classify the groupoid fibrations over log schemes that arise in this manner in terms of a categorical…

Algebraic Geometry · Mathematics 2011-03-14 W. D. Gillam

In this paper, we define the notion of crossed modules of groups with action and investigate related structures. Functions for computing of these structures have been written using the GAP computational discrete algebra programming…

Category Theory · Mathematics 2022-01-19 Alper Odabaş , Elis Soylu Yılmaz

All physical observations are made relative to a reference frame, which is a system in its own right. If the system of interest admits a group symmetry, the reference frame observing it must transform commensurately under the group to…

High Energy Physics - Theory · Physics 2024-07-03 Shadi Ali Ahmad , Wissam Chemissany , Marc S. Klinger , Robert G. Leigh

For an arbitrary localic etale groupoid G we provide simple descriptions, in terms of modules over the quantale O(G) of the groupoid, of the continuous actions of G, including actions on open maps and sheaves. The category of G-actions is…

Category Theory · Mathematics 2011-03-29 Pedro Resende

In this paper we study holomorphic actions of the complex multiplicative group on complex manifolds around a singular (fixed) point. We prove linearization results for the germ of action and also for the whole action under some conditions…

Complex Variables · Mathematics 2024-08-26 Víctor León , Bruno Scárdua

We consider crossed product von Neumann algebras arising from free Bogoljubov actions of the integers. We describe several presentations of them as amalgamated free products and cocycle crossed products and give a criterion for…

Operator Algebras · Mathematics 2012-12-14 Sven Raum

We unify and generalize several approaches to constructing braid group representations from finite groups, using iterated twisted tensor products. Our results hint at a relationship between the braidings on the $G$-gaugings of a pointed…

Quantum Algebra · Mathematics 2019-06-20 Paul Gustafson , Andrew Kimball , Eric C. Rowell , Qing Zhang

The second author showed how Katsura's construction of the C*-algebra of a topological graph E may be twisted by a Hermitian line bundle L over the edge space E. The correspondence defining the algebra is obtained as the completion of the…

Operator Algebras · Mathematics 2017-01-25 Alex Kumjian , Hui Li

All crossed products of two cyclic groups are explicitly described using generators and relations. A necessary and sufficient condition for an extension of a group by a group to be a cyclic group is given.

Group Theory · Mathematics 2014-02-24 Ana-Loredana Agore , Dragos Fratila

We introduce a method to study C*-algebras possessing an action of the circle group, from the point of view of its internal structure and its K-theory. Under relatively mild conditions our structure Theorem shows that any C*-algebra, where…

funct-an · Mathematics 2016-08-31 Ruy Exel

Let $(A,G,\alpha)$ be a partial dynamical system and let $A\rtimes_{\alpha,r} G$ denote the associated reduced partial crossed product. In this article, we introduce the Haagerup property for partial actions of discrete groups on…

Operator Algebras · Mathematics 2026-04-07 Md Amir Hossain , Chaitanya J. Kulkarni

Let $G$ be a group which admits a generating set consisting of finite order elements. We prove that any Hopf algebra which factorizes through the Taft algebra and the group Hopf algebra $K[G]$ (equivalently, any bicrossed product between…

Rings and Algebras · Mathematics 2019-08-27 A. L. Agore , L. Nastasescu