scholarly journals Certain congruence and quotient lattices related to completely 0-simple and primitive regular semigroups

1969 ◽  
Vol 10 (1) ◽  
pp. 21-24 ◽  
Author(s):  
H. E. Scheiblich
Keyword(s):  
Regular Semigroup ◽  
Simple Proof ◽  
Simple Semigroup ◽  
Chain Condition ◽  
Regular Semigroups ◽  
Lattice Of Congruences

G. Lallement [4] has shown that the lattice of congruences, Λ(S), on a completely 0-simple semigroupSis semimodular, thus improving G. B. Preston's result [5] that such a lattice satisfies the Jordan-Dedekind chain condition. More recently, J. M. Howie [2] has given a new and more simple proof of Lallement's result using work due to Tamura [9]. The purpose of this note is to extend the semimodularity result to primitive regular semigroups, to establish a theorem relating certain congruence and quotient lattices, and to provide a theorem for congruences on any regular semigroup.

scholarly journals Group congruences on eventually regular semigroups

1988 ◽  
Vol 45 (3) ◽  
pp. 320-325 ◽  
Author(s):  
S. Hanumantha Rao ◽  
P. Lakshmi
Keyword(s):  
Regular Semigroup ◽  
Group Congruence ◽  
Regular Semigroups ◽  
Eventually Regular Semigroup ◽  
Lattice Of Congruences

AbstractA characterization of group congruences on an eventually regular semigroup S is provided. It is shown that a group congruence is dually right modular in the lattice of congruences on S. Also for any group congruence ℸ and any congruence p on S, ℸ Vp and kernel ℸ Vp are described.

Regular Semigroups Which Are Amalgamation Bases for Finite Semigroups

2007 ◽  
Vol 14 (02) ◽  
pp. 245-254 ◽  
Author(s):  
Kunitaka Shoji
Keyword(s):  
Regular Semigroup ◽  
Simple Semigroup ◽  
Finite Semigroup ◽  
Principal Factor ◽  
Regular Semigroups ◽  
Completely Simple Semigroup ◽  
Finite Semigroups ◽  
Completely Simple ◽  
Finite Regular Semigroup

In this paper, we prove that a completely 0-simple (or completely simple) semigroup is an amalgamation base for finite semigroups if and only if it is an amalgamation base for semigroups. By adopting the same method as used in a previous paper, we prove that a finite regular semigroup is an amalgamation base for finite semigroups if its [Formula: see text]-classes are linearly ordered and all of its principal factor semigroups are amalgamation bases for finite semigroups. Finally, we give an example of a finite semigroup U which is an amalgamation base for semigroups, but not all of its principal factor semigroups are amalgamation bases either for semigroups or for finite semigroups.

scholarly journals On the lattice of congruences on a semilattice

1971 ◽  
Vol 12 (4) ◽  
pp. 456-460 ◽  
Author(s):  
T. E. Hall
Keyword(s):  
Simple Semigroup ◽  
Natural Extension ◽  
Chain Condition ◽  
Alternative Proof ◽  
Finite Lattices ◽  
Lattice Of Congruences

Lattices of congruences are studied in section II.6 of Cohn [2]. Papers [5] and [6] by Munn deal with lattices of congruences on semigroups and conditions under which these lattices are modular. In [4] Lallement shows that the lattice of congruences on a completely 0-simple semigroup is semimodular, giving an alternative proof of the result, due to Preston [7], that the lattice of congruences on a completely 0-simple semigroup satisfies a certain chain condition which is a natural extension to arbitrary lattices of the Jordan-Dedekind chain condition for finite lattices.

scholarly journals Congruence lattices of regular semigroups related to kernels and traces

1991 ◽  
Vol 34 (2) ◽  
pp. 179-203 ◽  
Author(s):  
Mario Petrich
Keyword(s):  
Distributive Lattice ◽  
Regular Semigroup ◽  
Homomorphic Image ◽  
Regular Semigroups ◽  
Generators And Relations ◽  
Congruence Lattices ◽  
Left And Right ◽  
Lattice Of Congruences

The kernel–trace approach to congruences on a regular semigroup S can be refined by introducing the left and right traces. This induces eight operators on the lattice of congruences on S: t1, k, tr,; Tt, K, Tr; t, T. We describe the lattice of congruences on S generated by six 3-element subsets of the set {ωt1, ωk, ωtr, εTt, εK, εTr} where ω and ε denote the universal and the equality relations. This is effected by means of a diagram and in terms of generators and relations on a free distributive lattice, or a homomorphic image thereof. We perform the same analysis for the lattice of congruences on S generated by the set {εK, ωk, εT, ωt}.

scholarly journals On the lattice of congruences on a regular semigroup

1969 ◽  
Vol 1 (2) ◽  
pp. 231-235 ◽  
Author(s):  
T. E. Hall
Keyword(s):  
Regular Semigroup ◽  
Complete Lattice ◽  
Inverse Semigroups ◽  
Natural Homomorphism ◽  
Lattice Homomorphism ◽  
Regular Semigroups ◽  
Lattice Of Congruences

A result of Reilly and Scheiblich for inverse semigroups is proved true also for regular semigroups. For any regular semigroup S the relation θ is defined on the lattice, Λ(S), of congruences on S by: (ρ, τ) ∈ θ if ρ and τ induce the same partition of the idempotents of S. Then θ is a congruence on Λ(S), Λ(S)/θ is complete and the natural homomorphism of Λ(S) onto Λ(S)/θ is a complete lattice homomorphism.

The word problem for the bifree combinatorial strict regular semigroup

1993 ◽  
Vol 113 (3) ◽  
pp. 519-533 ◽  
Author(s):  
Karl Auinger
Keyword(s):  
Regular Semigroup ◽  
Free Algebra ◽  
Simple Semigroup ◽  
Direct Products ◽  
Binary Relations ◽  
Free Object ◽  
Regular Semigroups ◽  
Binary Operations ◽  
Subdirect Products

AbstractA class of regular semigroups closed under taking direct products, regular subsemigroups and homomorphic images is ane(xistence)-variety of regular semigroups. The classof all combinatorial strict regular semigroups is thee-variety generated by the five element non-orthodox completely 0-simple semigroup and consists of all regular subdirect products of combinatorial completely 0-simple semigroups and/or rectangular bands. The bifree objecton the setXinis the natural concept of a ‘free object’ in the class.is generated by the setXand the set of formal inversesX′ under the two binary operations of multiplication · and forming the sandwich element ∧A. Henceis a homomorphic image of the absolutely free algebraof type 〈2, 2〉 generated by X ∪X′. In this paper we shall describe the associated congruence onF〈2, 2〉(X∪X′) and construct a model ofin terms of sets and binary relations. As an application, a model of the free strict pseudosemilattice on a setXis obtained.

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 Semimodularity and bisimple ω-semigroups

1970 ◽  
Vol 17 (1) ◽  
pp. 79-81 ◽  
Author(s):  
H. E. Scheiblich
Keyword(s):  
Simple Semigroup ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Primitive Idempotent ◽  
Necessary And Sufficient ◽  
Lattice Of Congruences

Let S be a completely 0-simple semigroup and let Λ(S) be the lattice of congruences on S. G. Lallement (2) has described necessary and sufficient conditions on S for Λ(S) to be modular, and has shown that Λ(S) is always semimodular . This result may be stated: If S is 0-bisimple and contains a primitive idempotent, then Λ(S) is semimodular.

scholarly journals Enlargements of regular semigroups

1996 ◽  
Vol 39 (3) ◽  
pp. 425-460 ◽  
Author(s):  
M. V. Lawson
Keyword(s):  
Regular Semigroup ◽  
Semigroup Theory ◽  
Regular Semigroups

We introduce a class of regular extensions of regular semigroups, called enlargements; a regular semigroup T is said to be an enlargement of a regular subsemigroup S if S = STS and T = TST. We show that S and T have many properties in common, and that enlargements may be used to analyse a number of questions in regular semigroup theory.

scholarly journals A special sublattice of the congruence lattice of a regular semigroup

1997 ◽  
Vol 40 (3) ◽  
pp. 457-472 ◽  
Author(s):  
Mario Petrich
Keyword(s):  
Distributive Lattice ◽  
Regular Semigroup ◽  
Congruence Lattice ◽  
Regular Semigroups ◽  
Generators And Relations ◽  
Completely Regular ◽  
Completely Simple Semigroups ◽  
Special Cases ◽  
Completely Regular Semigroups ◽  
Completely Simple

Let S be a regular semigroup and be its congruence lattice. For ρ ∈ , we consider the sublattice Lρ of generated by the congruences pw where w ∈ {K, k, T, t}* and w has no subword of the form KT, TK, kt, tk. Here K, k, T, t are the operators on induced by the kernel and the trace relations on . We find explicitly the least lattice L whose homomorphic image is Lρ for all ρ ∈ and represent it as a distributive lattice in terms of generators and relations. We also consider special cases: bands of groups, E-unitary regular semigroups, completely simple semigroups, rectangular groups as well as varieties of completely regular semigroups.

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