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The semigroups of unital extensions of separable $C^\ast$-algebras come in two flavours: a strong and a weak version. By the unital $\mathrm{Ext}$-groups, we mean the groups of invertible elements in these semigroups. We use the unital…

Operator Algebras · Mathematics 2019-03-15 James Gabe , Efren Ruiz

We introduce algebraic dynamical systems, which consist of an action of a right LCM semigroup by injective endomorphisms of a group. To each algebraic dynamical system we associate a C*-algebra and describe it as a semigroup C*-algebra. As…

Operator Algebras · Mathematics 2019-02-08 Nathan Brownlowe , Nadia S. Larsen , Nicolai Stammeier

In this paper we describe all, up to isomorphism, left unital, right unital and unital algebra structures on two-dimensional vector space over any algebraically closed field and $\mathbb{R}$. We tabulate the algebras with the units.

Rings and Algebras · Mathematics 2018-12-04 H. Ahmed , U. Bekbaev , I. Rakhimov

We introduce superequivalence and superuniform spaces.

Rings and Algebras · Mathematics 2018-11-06 William H. Rowan

Every semigroup containing an ideal subgroup is called a homogroup, and it is a grouplike if and only if it has only one central idempotent. On the other hand, a class of algebraic structures covering group-$e$-semigroups…

Group Theory · Mathematics 2024-10-02 M. H. Hooshmand

For the first time, we have introduced the concept of N-groups, N-semigroups, N-loops, and N-groupoids. We also define a mixed N-algebraic structure. The main aim of this book is to attract young mathematicians to this interesting field. It…

General Mathematics · Mathematics 2007-05-23 W. B. Vasantha Kandasamy , Florentin Smarandache

In this paper, new hyper-algebraic structures called polygroupoid, polyquasigroup and polyloop were introduced with concrete examples given. The first, second, third and fourth left (middle, right) nuclei of polygroupoid were introduced and…

Group Theory · Mathematics 2025-04-23 K. G. Ilori , T. G. Jaiyeola , O. O. Oyebola , O. B. Ogunfolu , E. A. Alhassan

We discuss some types of congruences on Menger algebras of rank $n$, which are generalizations of the principal left and right congruences on semigroups. We also study congruences admitting various types of cancellations and describe their…

Rings and Algebras · Mathematics 2015-01-27 Wieslaw A. Dudek , Valentin S. Trokhimenko

For a large class of finite-dimensional Lie superalgebras (including the classical simple ones) a Lie supergroup associated to the algebra is defined by fixing the Hopf superalgebra of functions on the supergroup. Then it is shown that on…

Rings and Algebras · Mathematics 2007-05-23 M. Scheunert , R. B. Zhang

We describe all finite subsemigroups of a free left regular band of infinite rank. Moreover, we show applications of this result in algebraic geometry and model theory.

Algebraic Geometry · Mathematics 2019-10-24 Artem N. Shevlyakov

We are interested in formulas for the number of elements in certain classes of numerical semigroups

Combinatorics · Mathematics 2014-10-28 Ernst Kunz , Rolf Waldi

An amalgam of inverse semigroups [S,T,U] is full if U contains all of the idempotents of S and T. We show that for a full amalgam [S,T,U], the C*-algebra of the inverse semigroup amaglam of S and T over U is the C*-algebraic amalgam of…

Operator Algebras · Mathematics 2010-07-08 Allan P Donsig , Steven P. Haataja , John C. Meakin

Given a group $X$ we study the algebraic structure of the compact right-topological semigroup $\lambda(X)$ consisting of maximal linked systems on $X$. This semigroup contains the semigroup $\beta(X)$ of ultrafilters as a closed…

Group Theory · Mathematics 2011-10-11 Taras Banakh , Volodymyr Gavrylkiv

In this paper, we introduce principally $\delta$-lifting modules which are analogous to $\delta$-lifting modules and principally $\delta$-semiperfect modules as a generalization of $\delta$-semiperfect modules and investigate their…

Rings and Algebras · Mathematics 2017-07-11 Hatice Inankil , Sait Halicioglu , A. Harmanci

We describe $\sigma$-matching, interchangeable and, as a consequence, totally compatible products on some classes of associative algebras, including unital algebras, the semigroup algebras of rectangular bands, algebras with enough…

Rings and Algebras · Mathematics 2025-10-22 Mykola Khrypchenko

In this work, the notion of a quantum inverse semigroup is introduced as a linearized generalization of inverse semigroups. Beyond the algebra of an inverse semigroup, which is the natural example of a quantum inverse semigroup, several…

Quantum Algebra · Mathematics 2023-04-03 Marcelo Muniz Alves , Eliezer Batista , Francielle Kuerten Boeing

In this expository article, we give a self-contained introduction to the wonderfully well-behaved class of pseudocompact algebras, focusing on the foundational classes of semisimple and separable algebras. We give characterizations of such…

Rings and Algebras · Mathematics 2025-01-20 Kostiantyn Iusenko , John MacQuarrie

We complete a classification of the two-vertex geometrically irreducible algebras. We also classify the algebras in new classes of hom- and ext-irreducible algebras.

Representation Theory · Mathematics 2024-05-08 Grzegorz Bobinski , Grzegorz Zwara

The study of open quantum systems relies on the notion of unital completely positive semigroups on $C^*$-algebras representing physical systems. The natural generalisation would be to consider the unital completely positive semigroups on…

Operator Algebras · Mathematics 2022-11-15 V. I. Yashin

Certain $*$-semigroups are associated with the universal $C^*$-algebra generated by a partial isometry, which is itself the universal $C^*$-algebra of a $*$-semigroup. A fundamental role for a $*$-structure on a semigroup is emphasized, and…

Operator Algebras · Mathematics 2014-06-03 Berndt Brenken