scholarly journals A simplistic approach to inverse transversals

1996 ◽  
Vol 39 (1) ◽  
pp. 57-69 ◽  
Author(s):  
T. S. Blyth ◽  
M. H. Almeida Santos
Keyword(s):  
Regular Semigroup ◽  
Inverse Transversal ◽  
Inverse Subsemigroup

An inverse transversal of a regular semigroup S is an inverse subsemigroup that contains precisely one inverse of each element of S. In the literature there are three known types of inverse transversal, namely those that are multiplicative, those that are weakly multiplicative, and those that form quasi-ideals. Here, by considering natural ways in which certain words can be simplified, we reveal four new types of inverse transversal. All of these can be illustrated nicely in examples that are based on 2 × 2 matrices.

scholarly journals On quasi-orthodox semigroups with inverse transversals

1997 ◽  
Vol 40 (3) ◽  
pp. 505-514 ◽  
Author(s):  
T. S. Blyth ◽  
M. H. Almeida Santos
Keyword(s):  
Regular Semigroup ◽  
Inverse Transversal ◽  
Inverse Subsemigroup ◽  
Orthodox Semigroups

An inverse transversal of a regular semigroup S is an inverse subsemigroup So that contains precisely one inverse of each element of S. Here we consider the case where S is quasi-orthodox. We give natural characterisations of such semigroups and consider various properties of congruences.

Regular semigroups with a multiplicative inverse transversal

1982 ◽  
Vol 92 (3-4) ◽  
pp. 253-270 ◽  
Author(s):  
T. S. Blyth ◽  
R. McFadden
Keyword(s):  
Regular Semigroup ◽  
Inverse Transversal ◽  
Multiplicative Inverse ◽  
Multiplicative Property ◽  
Regular Semigroups ◽  
Inverse Subsemigroup

SynopsisBy an inverse transversal of a regular semigroup S we mean an inverse subsemigroup that contains a single inverse of every element of S. A certain multiplicative property (which in the case of a band is equivalent to normality) is imposed on an inverse transversal and a complete description of the structure of S is obtained.

scholarly journals Construction of regular semigroups with inverse transversals

1989 ◽  
Vol 32 (1) ◽  
pp. 41-51 ◽  
Author(s):  
Tatsuhiko Saito
Keyword(s):  
Regular Semigroup ◽  
Unique Element ◽  
Inverse Transversal ◽  
Regular Semigroups ◽  
Inverse Subsemigroup

Let S be a regular semigroup. An inverse subsemigroup S° of S is an inverse transversal if |V(x)∩S°| = 1 for each x∈S, where V(x) denotes the set of inverses of x. In this case, the unique element of V(x)∩S° is denoted by x°, and x°° denotes (x°)–1. Throughout this paper S denotes a regular semigroup with an inverse transversal S°, and E(S°) = E° denotes the semilattice of idempotents of S°. The sets {e∈S:ee° = e} and {f∈S:f°f=f} are denoted by Is and Λs, respectively, or simply I and Λ. Though each element of these sets is idempotent, they are not necessarily sub-bands of S. When both I and Λ are sub-bands of S, S° is called an S-inverse transversal. An inverse transversal S° is multiplicative if x°xyy°∈E°, and S° is weakly multiplicative if (x°xyy°)°∈E° for every x, y∈S. A band B is left [resp. right] regular if e f e = e f [resp. e f e = f e], and B is left [resp. right] normal if e f g = e g f [resp. e f g = f e g] for every e, f, g∈B. A subset Q of S is a quasi-ideal of S if QSQ ⊆ S.

scholarly journals Congruences on orthodox semigroups with associate subgroups

1996 ◽  
Vol 38 (1) ◽  
pp. 113-124
Author(s):  
T. S. Blyth ◽  
Emília Giraldes ◽  
M. Paula O. Marques-Smith
Keyword(s):  
Regular Semigroup ◽  
Maximal Subgroup ◽  
Structure Theorem ◽  
Inverse Transversal ◽  
Similar Concept ◽  
Inverse Subsemigroup ◽  
Associate Subgroup ◽  
Orthodox Semigroups ◽  
Middle Unit

If Sis a regular semigroup then an inverse transversal of S is an inverse subsemigroup T with the property that |T ∩ V(x)| = 1 for every x ∈ S where V(x) denotes the set of inverses of x ∈ S. In a previous publication [1] we considered the similar concept of a subsemigroup T of S such that |T ∩ A(x)| = 1 for every x ∩ S where A(x) = {y∈ S;xyx = x} denotes the set of associates (or pre-inverses) of x ∈ S, and showed that such a subsemigroup T is necessarily a maximal subgroup Ha for some idempotent α ∈ S. Throughout what follows, we shall assume that S is orthodox and α is a middle unit (in the sense that xαy = xy for all x, y ∈ S). Under these assumptions, we obtained in [1] a structure theorem which generalises that given in [3] for uniquely unit orthodox semigroups. Adopting the notation of [1], we let T ∩ A(x) = {x*} and write the subgroup T as Hα = {x*;x ∈ S}, which we call an associate subgroup of S. For every x ∈ S we therefore have x*α = x* = αx* and x*x** = α = x**x*. As shown in [1, Theorems 4, 5] we also have (xy)* = y*x* for all x, y ∈ S, and e* = α for every idempotent e.

scholarly journals Naturally ordered regular semigroups with maximum inverses

1989 ◽  
Vol 32 (1) ◽  
pp. 33-39 ◽  
Author(s):  
Tatsuhiko Saito
Keyword(s):  
Regular Semigroup ◽  
Sufficient Condition ◽  
Necessary And Sufficient Condition ◽  
Inverse Transversal ◽  
Regular Semigroups ◽  
Inverse Subsemigroup ◽  
Necessary And Sufficient

Let S be a regular semigroup. An inverse subsemigroup S° of S is called an inverse transversal if S° contains a unique inverse of each element of S. An inverse transversal S° of S is called multiplicative if x°xyy° is an idempotent of S° for every x, y∈S, where x° denotes the unique inverse of x∈S in S°. In Section 1, we obtain a necessary and sufficient condition in order for inverse transversals to be multiplicative.

scholarly journals On weakly multiplicative inverse transversals

1994 ◽  
Vol 37 (1) ◽  
pp. 91-99 ◽  
Author(s):  
T. S. Blyth ◽  
M. H. Almeida Santos
Keyword(s):  
Regular Semigroup ◽  
Inverse Transversal ◽  
Multiplicative Inverse

We show that an inverse transversal of a regular semigroup is multiplicative if and only if it is both weakly multiplicative and a quasi-ideal. Examples of quasi-ideal inverse transversals that are not multiplicative are known. Here we give an example of a weakly multiplicative inverse transversal that is not multiplicative. An interesting feature of this example is that it also serves to show that, in an ordered regular semigroup in which every element x has a biggest inverse x0, the mapping x↦x00 is not in general a closure; nor is x↦x** in a principally ordered regular semigroup.

scholarly journals Regular semigroups, fundamental semigroups and groups

1980 ◽  
Vol 29 (4) ◽  
pp. 475-503 ◽  
Author(s):  
D. B. McAlister
Keyword(s):  
Regular Semigroup ◽  
Partial Order ◽  
Direct Product ◽  
Homomorphic Image ◽  
Sufficient Conditions ◽  
Main Tool ◽  
Natural Partial Order ◽  
Regular Semigroups ◽  
Necessary And Sufficient ◽  
Fundamental Semigroups

AbstractIn this paper we obtain necessary and sufficient conditions on a regular semigroup in order that it should be an idempotent separating homomorphic image of a full subsemigroup of the direct product of a group and a fundamental or combinatorial regular semigroup. The main tool used is the concept of a prehomomrphism θ: S → T between regular semigroups. This is a mapping such that (ab) θ ≦ aθ bθ in the natural partial order on T.

scholarly journals FACTORIZATION THEOREMS FOR MORPHISMS OF ORDERED GROUPOIDS AND INVERSE SEMIGROUPS

2001 ◽  
Vol 44 (3) ◽  
pp. 549-569 ◽  
Author(s):  
Benjamin Steinberg
Keyword(s):  
Inverse Semigroup ◽  
Regular Semigroup ◽  
Classical Theory ◽  
Derived Category ◽  
Inverse Semigroups ◽  
Subject Classification

AbstractAdapting the theory of the derived category to ordered groupoids, we prove that every ordered functor (and thus every inverse and regular semigroup homomorphism) factors as an enlargement followed by an ordered fibration. As an application, we obtain Lawson’s version of Ehresmann’s Maximum Enlargement Theorem, from which can be deduced the classical theory of idempotent-pure inverse semigroup homomorphisms and $E$-unitary inverse semigroups.AMS 2000 Mathematics subject classification: Primary 20M18; 20L05; 20M17

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