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Given an action of a groupoid by isomorphisms on a Fell bundle (over another groupoid), we form a semidirect-product Fell bundle, and prove that its $C^{*}$-algebra is isomorphic to a crossed product.

Operator Algebras · Mathematics 2021-12-30 Lucas Hall , S. Kaliszewski , John Quigg , Dana P. Williams

We consider a large family of product operations of formal power series in noncommuting indeterminates, the classes of automata they define, and the respective equivalence problems. A $P$-product of series is defined coinductively by a…

Formal Languages and Automata Theory · Computer Science 2026-05-14 Lorenzo Clemente

Infinite products, indexed by countably infinite linear orders, arise naturally in the context of fundamental groupoids. Such products are called "transfinite" if the index orders are permitted to contain a dense suborder and are called…

Algebraic Topology · Mathematics 2025-01-27 Jeremy Brazas

Let $G$ be a finite group with $k$ conjugacy classes, and $S(\infty)$ be the infinite symmetric group, i.e. the group of finite permutations of $\left\{1,2,3,\ldots\right\}$. Then the wreath product $G_{\infty}=G\sim S(\infty)$ of $G$ with…

Representation Theory · Mathematics 2026-05-08 Eugene Strahov

We characterise the group property of being with infinite conjugacy classes for wreath products of groups

Group Theory · Mathematics 2007-05-23 Jean-Philippe Preaux

The aim of this paper is to investigate whether the class of automaton semigroups is closed under certain semigroup constructions. We prove that the free product of two automaton semigroups that contain left identities is again an automaton…

Group Theory · Mathematics 2015-10-09 Tara Brough , Alan J. Cain

In this article we use semigroupoids to describe a notion of algebraic bundles, mostly motivated by Fell ($C^*$-algebraic) bundles, and the sectional algebras associated to them. As the main motivational example, Steinberg algebras may be…

Rings and Algebras · Mathematics 2019-06-14 Luiz Gustavo Cordeiro

We develop a theory of twisted actions of categorical groups using a notion of semidirect product of categories. We work through numerous examples to demonstrate the power of these notions. Turning to representations, which are actions that…

Category Theory · Mathematics 2014-09-02 Saikat Chatterjee , Amitabha Lahiri , Ambar N. Sengupta

We consider the transfer functions describing the input-output relation for a class of linear open quantum systems involving feedback with nonzero time delays. We show how such transfer functions can be factorized into a product of terms…

Quantum Physics · Physics 2018-04-10 Gil Tabak , Ryan Hamerly , Hideo Mabuchi

We give a self-contained and simplified presentation of the theory of covariant representations for inverse semigroup actions on Banach algebras, which was recently introduced in the authors and A. Mckee in the twisted case. The main result…

Functional Analysis · Mathematics 2026-01-22 K. Bardadyn , B. K. Kwaśniewski

We propose a generalization of the external direct product concept to polyadic algebraic structures which introduces novel properties in two ways: the arity of the product can differ from that of the constituents, and the elements from…

Rings and Algebras · Mathematics 2022-04-12 Steven Duplij

A \emph{loop} $(B,\cdot)$ is a set $B$ together with a binary operation $\cdot$ such that (i) for each $a\in B$, the left and right translation mappings $L_{a}:B\to B: x \mapsto a\cdot x$ and $R_{a}:B\to B: x \mapsto x\cdot a$ are…

Group Theory · Mathematics 2007-05-23 Oliver Jones , Michael K. Kinyon

By a 2-group we mean a groupoid equipped with a weakened group structure. It is called split when it is equivalent to the semidirect product of a discrete 2-group and a one-object 2-group. By a permutation 2-group we mean the 2-group…

Category Theory · Mathematics 2014-02-05 Josep Elgueta

In [F. Caselli, Involutory reflection groups and their models, J. Algebra 24 (2010), 370--393] it is constructed a uniform Gelfand model for all non-exceptional irreducible complex reflection groups which are involutory. This model can be…

Combinatorics · Mathematics 2010-07-19 Fabrizio Caselli , Roberta Fulci

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

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

In this paper we prove some general theorems about representations of finite groups arising from the inner semidirect product of groups. We show how these results can be used for standard applications of group theory in quantum chemistry…

General Physics · Physics 2014-02-17 Marco A. S. Trindade

We consider group-subgroup pairs in which the group is a semidirect product and the subgroup is contained in the normal part. We give conditions for the pair to be a Hecke pair and we show that the enveloping Hecke algebra and Hecke…

Operator Algebras · Mathematics 2007-05-23 Marcelo Laca , Nadia S. Larsen

We introduce a new technique to prove connectivity of subsets of covering spaces (so called inductive connectivity), and apply it to Galois theory of problems of enumerative geometry. As a model example, consider the problem of permuting…

Algebraic Geometry · Mathematics 2020-03-03 Alexander Esterov , Lionel Lang

Here we generalize the concept of spatial tensor product, introduced by Skeide, of two product systems via a pair of normalized units. This new notion is called amalgamated tensor product of product systems, and now the amalgamation can be…

Operator Algebras · Mathematics 2014-05-16 B. V. Rajarama Bhat , Mithun Mukherjee