Archimedeaness and additive utility on totally ordered semigroups

We study problems concerning the existence of additive utility funtions defined on totally ordered semigroups. The existence of an additive utility function on a semigroup is characterized by means of conditions that are similar, but not equivalent, to Archimedeaness. This fact is used to analyze the existence of utility representations (not necessarily additive) on totally ordered Abelian groups. In this direction, we show that the positive cone of a representable totally ordered Abelian group admits a countable partition into Archimedean semigroups. All the semigroups in that partition are representable by means of a utility function, but at most one is additively representable. Communicated by M. W. Mislove     

The intertwining lifting theorem for ordered groups

Sz.-Nagy's dilation theorem for a contraction on a Hilbert space has been extended by Mlak to the case of a contraction semigroup whose indices are the positive elements of a totally ordered discrete group. We generalize to this case the intertwining lifting theorem of Sz.-Nagy and Foias. Some previous interpolation results on ordered groups are obtained as consequences.     

On a Class of Lattice Ordered Inverse Semigroups

It is well known that the free group on a non-empty set can be totally ordered and, further, that each compatible latttice ordering on a free group is a total ordering. On the other hand, Saitô has shown that no non-trivial free inverse semigroup can be totally ordered. In this note we show, however, that every free inverse monoid admits compatible lattice orderings which are closely related to the total orderings on free groups.These orderings are natural in the sense that the imposed partial ordering on the idempotents coincides with the natural partial ordering. For this to happen in a lattice ordered inverse semigroup, the idempotents must form a distributive lattice. The method of construction of the lattice orderings on free inverse monoids can be applied to show that naturally lattice ordered inverse semigroups with a given distributive lattice E of idempotents can have arbitrary Green's relation structure. Analogous results hold for naturally -semilatticed inverse semigroups. In this case, there is no restriction on the semilattice E of idempotents.We also show that every compatible lattice ordering on the free monogenic inverse monoid is of the type considered here. This permits us to prove that there are precisely eight distinct compatible lattice orderings on this semigroup. They belong to two families, each of which contains four members, of conjuguate lattice orderings.     

Compact semitopological inverse Clifford Semigroups

An inverse Clifford Semigroup is a semilattice of groups. Conditions are given for constructing a compact semitopological (separately continuous multiplication) inverse Clifford semigroup on a compact Hausdorff semilattice. The conditions are necessary and sufficient for decomposing a compact inverse Clifford semigroup containing a dense subgroup and locally compact maximal groups into its semilattice of groups. A catalogue of examples is given to demonstrate the construction while exhibiting various pathologies. This work was supported in part by the S.R.C.     

Sur les demi-groupes reticules et les o-demi-groupes

A necessary and sufficient condition is given in order that a lattice-ordered semigroup admit a totally ordered ?-homomorphic image (Theorem 1). This permits us to give (Theorem 2) a necessary and sufficient condition that a lattice-ordered semigroup be representable, that is, that it be ?-isomorphic to a subdirect product of totally ordered semigroups, thereby solving a problem posed by L. Fuchs ([2], p. 289). We also establish a necessary and sufficient condition that a semigroup be an o-semigroup, that is, that it admit a structure of totally ordered semigroup (Theorem 3).     

半格序Clifford半群

证明了每一个半格序Clifford半群都能嵌入到其加法半群的半格序自同态半群当中;给出了同余单的半格序Clifford半群所具有的几种形式,得到了自然半格序零群是仅有的次直不可约自然半格序Clifford半群.     

具有Clifford断面的纯正半群

本文研究有Clifford断面的纯正半群.为了获得主要的结构定理，证明了纯正半群有群断面当且仅当它是矩形群;利用半格和矩形带，建立了有Clifford断面的纯正半群的结构.     

Some conditions for hypervaluability of a ring by a totally ordered semigroup

The purpose of this paper is to give some conditions for a ring to be hyperbaluable by a totally ordered semigroup. In § 1 we give some preliminary definitions and results, and a bibliographical note. The theorem in § 2 provides a sufficient condition for hypervaluability. The theorem in § 3 provides a necessary and sufficient condition for hypervaluability. In § 4 we provide an example of a ring satisfying the conditions of theorem 2 and is therefore hypervaluable by a totally ordered semigroup.     

含幺Clifford半群上的Rees矩阵半群的同余和正规加密群结构

给出了含幺Clifford半群上的Rees矩阵半群S的正规加密群结构,证明了在含幺Clifford半群上的Rees矩阵半群S上以下两个条件是等价的:(1)S上的同余ρ是完全单半群同余;(2)S上的同余ρ和S上的相容组之间存在保序双射.最后还证明了S上的完全单半群同余所构成的同余格是半模的.     

On the additive structure of a class of ordered semirings

In this paper we shall determine the additive structure of totally ordered semirings if its multiplicative structure is a right naturally ordered o-Archimedean semigroup.     

一类Clifford半群的刻画

G是一个群,I是一个指标集.令CG=G×I={(g,i):g∈G,i∈I};(a,i)(b,j)=(ab,k)with k=min{i,j}则CG是一个半群.事实上,CG是Clifford半群,并且CG代表了一类特殊的Clifford半群.     

A generalized Clifford theorem of semigroups

A U-abundant semigroup S in which every H-class of S contains an element in the set of projections U of S is said to be a U-superabundant semigroup.This is an analogue of regular semigroups which are unions of groups and an analogue of abundant semigroups which are superabundant.In 1941,Clifford proved that a semigroup is a union of groups if and only if it is a semilattice of completely simple semigroups.Several years later,Fountain generalized this result to the class of superabundant semigroups.In this p...     

Clifford semigroups as functors and their cohomology

We prove that the category of Clifford semigroups and prehomomorphisms CSP\mathcal{CSP} is isomorphic to a certain subcategory of the category of diagrams over groups. Under this isomorphism, Clifford semigroups are identified with certain functors. As an application of the isomorphism theorem, we show that the category with objects commutative inverse semigroups having the same semilattice of idempotents and with morphisms, the inverse semigroup homomorphisms that fix the semilattice, imbeds into a category of right modules over a certain ring. Also we find a very close relationship between the cohomology groups of a commutative inverse monoid and the cohomology groups of the colimit group of the functor giving the monoid.     

Structure of Quantum Doubles of Finite Clifford Monoids

Abstract

In this paper, over a field k, we give the structure theorem of the quantum double of a finite Clifford monoid through bicrossed products and quantum doubles of groups. By this result, it is shown that the quantum double of a finite Clifford monoid is semisimple (resp. von Neumann regular) if and only if the semigroup is a finite group and the characteristic p of k does not divide the order of this group.     

Clifford半群的E-扩张

半群扩张是以已知的或者较简单的半群类为基础,借助某种方法扩张成一类半群.本文讨论Cliffbrd半群借助Mum半群TE的扩张.引入了这种扩张的概念并给出一个具体的例子.还给出Clifford半群有E扩张的必要条件.证明了满逆半群的Green关系等价类在Munn表示下的同态象仍是同样的等价类.     

Characterizations of totally ordered sets by their various endomorphisms

We characterize totally ordered sets within the class of all ordered sets containing at least three-element chains using a simple relationship between their isotone transformations and the so called 2-, 3-, 4-endomorphisms which are introduced in the paper. Another characterization of totally ordered sets within the class of ordered sets of a locally finite height with at least four-element chains in terms of the regular semigroup theory is also given.     

一类广义变换半群的格林关系

设X是一个全序集,E是X上的一个凸等价关系．令 OE（X）={f∈TE（X）：Ax,y∈X,x≤y→f（x）≤f（y））, 其中TE（X）是E-保持变换半群．对于取定的θ∈OE（X）,在OE（X）上定义运算fog=fθg,使OE（X）成为广义半群OE（X;θ）．对于有限全序集X上的凸等价关系E,本文刻画了广义半群OE（X;θ）的正则元,描述了这个半群的格林关系．     

Various notions of weak injectivity over Clifford semigroups

We study various notions of weak injectivity of acts over a Clifford semigroup. In addition we characterize weak self-injectivities of several classes of Clifford semigroups constructed via particular kinds of groups and group homomorphisms. Research of X. Zhang supported by the China Scholarship Council No. 2006101056. Research of Y. Wang supported by National Natural Science Foundation of China Research Grant 10571181.     

关于Clifford半群上的fuzzy同余

利用半群fuzzy同余的概念,讨论一类特殊的完全正则半群,即Clifford半群上的fuzzy同余.研究该类半群上fuzzy同余的性质.在此基础上,给出Clifford半群上fuzzy同余的性质和特征,得到Cllifford半群上fuzzy同余为fuzzy消去同余的充要条件.