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We present some constructions of groupoids as: direct product, semidirect product, and we give necessary and sufficient conditions for a groupoid to be embedded into a direct product of groupoids. Also, we establish necessary and sufficient…

Category Theory · Mathematics 2021-01-01 Víctor Marín , Héctor Pinedo

We introduce semidirect products of skew monoidal categories as a categorification of semidirect products of monoids (or, perhaps more familiarly, of groups). We also discuss how this construction interacts with monoidal, autonomous and…

Category Theory · Mathematics 2016-07-05 Ben Fuller

We construct categorical braid group actions from 2-representations of a Heisenberg algebra. These actions are induced by certain complexes which generalize spherical (Seidel-Thomas) twists and are reminiscent of the Rickard complexes…

Representation Theory · Mathematics 2019-02-20 Sabin Cautis , Anthony Licata , Joshua Sussan

In this note we observe that the notion of an induced representation has an analog for quasi-actions. We then use induced quasi-actions to refine some earlier rigidity results for product spaces.

Group Theory · Mathematics 2008-01-22 Bruce Kleiner , Bernhard Leeb

We introduce a notion of c-group, which is a group up to congruence relation and consider the corresponding category. Extensions, actions and crossed modules (c-crossed modules) are defined in this category and the semi-direct product is…

Category Theory · Mathematics 2020-12-11 Tamar Datuashvili , Osman Mucuk , Tunçar Şahan

Ostrowski's theorem implies that $\log(x),\log(x+1),\ldots$ are algebraically independent over $\mathbb{C}(x)$. More generally, for a linear differential or difference equation, it is an important problem to find all algebraic dependencies…

Commutative Algebra · Mathematics 2019-08-15 Alexey Ovchinnikov , Michael Wibmer

In this paper we continue the study of groups of trace class and consider in particular the case of semi-direct products. One of the highlights is the theorem saying that the semi-direct product of a semisimple Lie group G and its Lie…

Representation Theory · Mathematics 2018-01-31 Gerrit van Dijk

Topological algebras have properties that extend naturally to those of topological groups [8, 9], but is it the case that semi-direct products exist as in the category of groups? Firstly, we express concepts in categorical language that…

Category Theory · Mathematics 2013-11-06 Lucas Earl

We investigate continuous transitive actions of semitopological groups on spaces, as well as separately continuous transitive actions of topological groups.

General Topology · Mathematics 2019-08-15 Jan van Mill , Vesko Valov

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

In this paper, we consider topological semigroup actions on compact topological spaces. Under mild assumptions on the semigroup and the action, we construct a semi-direct product groupoid with a Haar system. We also show that it is…

Operator Algebras · Mathematics 2014-06-20 Jean Renault , S. Sundar

Given a group G, we construct, in a canonical way, an inverse semigroup S(G) associated to G. The actions of S(G) are shown to be in one-to-one correspondence with the partial actions of G, both in the case of actions on a set, and that of…

funct-an · Mathematics 2008-02-03 Ruy Exel

We introduce partial semigroupoid actions on sets and demonstrate that each such action admits universal globalization. Our construction extends the universal globalization for partial category actions given by P. Nystedt (Lundstr\"om) and…

Rings and Algebras · Mathematics 2025-12-11 Rafael Haag Petasny , Thaísa Tamusiunas

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

This paper aims to introduce a more general definition of quasirandom groups and generalize several well-known results in the literature in this new setting. More precisely, let $G$ be a semi-direct product of groups and $X\subseteq G$, we…

Combinatorics · Mathematics 2023-08-28 Thang Pham , Boqing Xue

Let G be a reductive group (over an algebraically closed field) equipped with the metaplectic data. In this paper we study the corresponding twisted Whittaker category for G. We construct and study a functor from the latter category to the…

Representation Theory · Mathematics 2023-08-25 Sergey Lysenko

This article focuses on those aspects about partial actions of groups which are related to Schur's theory on projective representations. It provides an exhaustive description of the partial Schur multiplier, and this result is achieved by…

Group Theory · Mathematics 2017-11-21 Mikhailo Dokuchaev , Nicola Sambonet

Quasi-conformal actions were introduced in the physics literature as a generalization of the familiar fractional linear action on the upper half plane, to Hermitian symmetric tube domains based on arbitrary Jordan algebras, and further to…

High Energy Physics - Theory · Physics 2009-11-13 Murat Gunaydin , Andrew Neitzke , Oleksandr Pavlyk , Boris Pioline

We introduce a notion of relative commutator -- an important special case being commutators twisted by an action -- as a straightforward modification of the definition of the Higgins commutator, establish its relation with a new notion of…

Category Theory · Mathematics 2024-10-10 Bo Shan Deval , Tim Van der Linden

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