Maximality properties of some subsemigroups of Baer-Levi semigroups

Communicated by Lásżló Márki     

奇异保序变换半群的极大正则子半群

设On为通常的有限链Xn={1,2,…,n}上的奇异保序变换半群.文中利用格林关系的方法讨论On的极大正则子半群,确定了On的所有的极大正则子半群.     

Locally maximal idempotent-generated subsemigroups of singular orientation-preserving transformation semigroups

In this paper we study locally maximal idempotent-generated subsemigroups of finite singular orientation-preserving transformation semigroups. This work is supported by N.S.F. and E.S.F. of Guizhou.     

A classification of maximal subsemigroups of finite order-preserving transformation semigroups

We describe the maximal subsemigroups of the semigroup of all order-preserving transformations of a finite chain and completely obtain their classification. We also count the number of its maximal subsemigroups.     

A classification of the maximal idempotent-generated subsemigroups of finite singular semigroups

We describe the maximal idempotent-generated subsemigroups of the finite singular semigroup Sing _n on the finite set X _n ={1,2, \ldots,n} , and count the number of its maximal idempotent-generated subsemigroups. October 21, 1999     

A classification of maximal idempotent-generated subsemigroups of singular orientation-preserving transformation semigroups

We describe maximal idempotent-generated subsemigroups of finite singular orientation-preserving transformation semigroups and completely obtain their classification. This work is supported by N.S.F. and E.S.F. of Guizhou.     

Free idempotent generated semigroups: subsemigroups,retracts and maximal subgroups

Let S be a subsemigroup of a semigroup T and let IG(E) and IG(F) be the free idempotent generated semigroups over the biordered sets of idempotents of E of S and F of T, respectively. We examine the relationship between IG(E) and IG(F), including the case where S is a retract of T. We give su?cient conditions satisfied by T and S such that for any e∈E, the maximal subgroup of IG(E) with identity e is isomorphic to the corresponding maximal subgroup of IG(F). We then apply this result to some special cases and, in particular, to that of the partial endomorphism monoid PEnd A and the endomorphism monoid EndA of an independence algebra A of finite rank. As a corollary, we obtain Dolinka’s reduction result for the case where A is a finite set.     

A classification of maximal idempotent-generated subsemigroups of finite orientation-preserving singular partial transformation semigroups

In this paper we describe the maximal idempotent-generated subsemigroups of the finite orientation-preserving singular partial transformation semigroup SPOP _n and obtain their complete classification. We also obtain a classification of the maximal idempotent-generated subsemigroups of the finite order-preserving singular partial transformation semigroup PO^k_n\mathit{PO}^{k}_{n} with respect to ≤ _k .     

Some properties of Umar semigroups: isomorphism theorems,ranks and maximal inverse subsemigroups

In a paper published in 1994, Umar defined an interesting class of transformation semigroups which naturally generalizes the Vagner one-point completion of the symmetric inverse semigroup. In this paper we prove some isomorphism theorems for finite such semigroups and compute their ranks. Moreover, we determine all maximal inverse subsemigroups of an arbitrary transformation semigroup of this type which is not inverse.     

On optimal factorization of free semigroups into free subsemigroups

Optimal factorizations of a subsemigroup into very pure and weakly prefix subsemigroups are considered. It is shown that the intersection of the family of very pure (weakly prefix) subsemigroups containing a given subset A of X⁺ is itself a very pure (weakly prefix) subsemigroup and procedures for constructing the basis of such minimal subsemigroups are provided.     

Ring semigroups whose subsemigroups intersect

A multiplicative semigroup S is said to be a ring semigroup provided there exists an addition + on S such that (S,+,⋅) is a ring. In this note, we characterize the ring semigroups S with the property that every two nonzero subsemigroups intersect.