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1.
It is proved that any pseudovariety of finite semigroups generated by inverse semigroups, the subgroups of which lie in some
proper pseudovariety of groups, does not contain all aperiodic semigroups with commuting idempotents. In contrast we show
that every finite semigroup with commuting idempotents divides a semigroup of partial bijections that shares the same subgroups.
Finally, we answer in the negative a question of Almeida as to whether a result of Stiffler characterizing the semidirect
product of the pseudovarieties ofR-trivial semigroups and groups applies to any proper pseudovariety of groups. 相似文献
2.
Vitor H. Fernandes 《Semigroup Forum》1998,56(3):418-433
NO of all normally ordered inverse semigroups. We show that the pseudovariety of inverse semigroups PCS generated by all semigroups of injective and order partial transformations on a finite chain consists of all aperiodic elements
of NO . Also, we prove that NO is the join pseudovariety of inverse semigroups. PCS V G , where G is the pseudovariety of all finite groups. 相似文献
3.
José Carlos Costa 《Semigroup Forum》2001,64(1):12-28
This paper is concerned with the computation of pseudovariety joins involving the pseudovariety L I of locally trivial semigroups. We compute, in particular, the join of L I with any subpseudovariety of CR(m in circle)N, the Mal’cev product of the pseudovariety of completely regular semigroups and the pseudovariety of nilpotent semigroups. Similar studies are conducted for the pseudovarieties K, D and N, where K (resp. D) is the pseudovariety of all semigroups S such that eS=e (resp. Se=e ) for each idempotent e of S . 相似文献
4.
José Carlos Costa 《Semigroup Forum》2002,64(1):12-28
This paper is concerned with the computation of pseudovariety joins involving the pseudovariety L I of locally trivial semigroups. We compute, in particular, the join of L I with any subpseudovariety of CR(m in circle)N, the Mal'cev product of the pseudovariety of completely regular semigroups
and the pseudovariety of nilpotent semigroups. Similar studies are conducted for the pseudovarieties K, D and N, where K (resp.
D) is the pseudovariety of all semigroups S such that eS=e (resp. Se=e ) for each idempotent e of S .
May 5, 1999 相似文献
5.
6.
A. Moura 《Semigroup Forum》2012,85(1):169-181
Generalizing a property of the pseudovariety of all aperiodic semigroups observed by Tilson, we call E -local a pseudovariety V which satisfies the following property: for a finite semigroup, the subsemigroup generated by its idempotents belongs to V if and only if so do the subsemigroups generated by the idempotents in each of its regular $\mathcal{D}$ -classes. In this paper, we present several sufficient or necessary conditions for a pseudovariety to be E-local or for a pseudoidentity to define an E-local pseudovariety. We also determine several examples of the smallest E-local pseudovariety containing a given pseudovariety. 相似文献
7.
《代数通讯》2013,41(7):2609-2615
Abstract Regular semigroups S with the property eS ? Se or Se ? eS for all idempotents e ∈ S include all left and right Clifford semigroups. Characterizations of such semigroups are given and their structure investigated, in particular in terms of spined products of left and right Clifford semigroups with respect to Clifford semigroups. 相似文献
8.
幂等元位于中心的半群的局部化和最小幂幺半群同余 总被引:1,自引:1,他引:0
李刚 《纯粹数学与应用数学》2006,22(1):6-8
局部化是交换代数的重要工具[1],证明幂等元位于中心的半群在其幂等元半格上的局部化存在且唯一,并给出此类半群的最小幂幺半群同余.另外,给出了若干半群的重要同余的刻划. 相似文献
9.
ABSTRACT The investigation of regular F-abundant semigroups is initiated. In fact, F-abundant semigroups are generalizations of regular cryptogroups in the class of abundant semigroups. After obtaining some properties of such semigroups, the construction theorem of the class of regular F-abundant semigroups is obtained. In addition, we also prove that a regular F-abundant semigroup is embeddable into a semidirect product of a regular band by a cancellative monoid. Our result is an analogue of that of Gomes and Gould on weakly ample semigroups, and also extends an earlier result of O'Carroll on F-inverse semigroups. 相似文献
10.
It is well known that if two algebraic structures A and B are residually finite then so is their direct product. Here we discuss the converse of this statement. It is of course true
if A and B contain idempotents, which covers the case of groups, rings, etc. We prove that the converse also holds for semigroups even
though they need not have idempotents. We also exhibit three examples which show that the converse does not hold in general.
相似文献
11.
We use classical results on the lattice of varieties of band (idempotent) semigroups to obtain information on the structure of the lattice Ps (DA) of subpseudovarieties of DA, – where DA is the largest pseudovariety of finite semigroups in which all regular semigroups are band semigroups. We bring forward a
lattice congruence on Ps (DA), whose quotient is isomorphic to , and whose classes are intervals with effectively computable least and greatest members. Also we characterize the pro-identities
satisfied by the members of an important family of subpseudovarieties of DA. Finally, letting V
k
be the pseudovariety generated by the k-generated elements of DA (k≥ 1), we use all our results to compute the position of the congruence class of V
k
in .
Received April 24, 1996; accepted in final form April 3, 1997. 相似文献
12.
13.
具有弱正规幂等元的富足半群的结构 总被引:7,自引:1,他引:6
本文研究含弱正规幂等元的富足半群.在给出这类半群的若干特征后,建立了具有弱正规幂等元的富足半群的结构.作为应用,给出具有正规幂等元的富足半群和具有(弱)正规幂等元的拟适当半群的结构. 相似文献
14.
In this article, we study commutative zero-divisor semigroups determined by graphs. We prove that for all n ≥ 4, the complete graph K n together with two end vertices has a unique corresponding zero-divisor semigroup, while the complete graph K n together with three end vertices has no corresponding semigroups. We determine all the twenty zero-divisor semigroups whose zero-divisor graphs are the complete graph K 3 together with an end vertex. 相似文献
15.
In this paper we study the congruences of *-regular semigroups, involution semigroups in which every element is p-related
to a projection (an idempotent fixed by the involution). The class of *-regular semigroups was introduced by Drazin in 1979,
as the involutorial counterpart of regular semigroups. In the standard approach to *-regular semigroup congruences, one ,starts
with idempotents, i.e. with traces and kernels in the underlying regular semigroup, builds congruences of that semigroup,
and filters those congruences which preserve the involution. Our approach, however, is more evenhanded with respect to the
fundamental operations of *-regular semigroups. We show that idempotents can be replaced by projections when one passes from
regular to *-regular semigroup congruences. Following the trace-kernel balanced view of Pastijn and Petrich, we prove that
an appropriate equivalence on the set of projections (the *-trace) and the set of all elements equivalent to projections (the
*-kernel) fully suffice to reconstruct an (involution-preserving) congruence of a *-regular semigroup. Also, we obtain some
conclusions about the lattice of congruences of a *-regular semigroup.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
17.
We consider the question of membership of A ∨ G, where A and G are the pseudovarieties of finite aperiodic semigroups, and finite groups, respectively. We find a straightforward criterion
for a semigroup S lying in a class of finite semigroups that are weakly abundant, to be in A ∨ G. The class of weakly abundant semigroups contains the class of regular semigroups, but is much more extensive; we remark
that any finite monoid with semilattice of idempotents is weakly abundant. To study such semigroups we develop a number of
techniques that may be of interest in their own right. 相似文献
18.
The notion of hyperdecidability has been introduced by the firstauthor as a tool to prove decidability of semidirect productsof pseudovarieties of semigroups. In this paper we considersome stronger notions which lead to improved decidability resultsallowing us in turn to establish the decidability of some iteratedsemidirect products. Roughly speaking, the decidability of asemidirect product follows from a mild, commonly verified propertyof the first factor plus the stronger property for all the otherfactors. A key role in this study is played by intermediatefree semigroups (relatively free objects of expanded type lyingbetween relatively free and relatively free profinite objects).As an application of the main results, the decidability of theKrohnRhodes (group) complexity is shown to follow fromnon-algorithmic abstract properties likely to be satisfied bythe pseudovariety of all finite aperiodic semigroups, therebysuggesting a new approach to answer (affirmatively) the questionas to whether complexity is decidable. 1991 Mathematics SubjectClassification: primary 20M05, 20M07, 20M35; secondary 08B20. 相似文献
19.
Roman S. Gigoń 《代数通讯》2017,45(7):3045-3051
We show that an exponential epigroup is a band of unipotent exponential epigroups (in which the set of idempotents forms a subsemigroup). Also, we investigate the structure of unipotent exponential epigroups. In addition, a characterization of the least normal band of groups congruence is given for an arbitrary medial epigroup. It is also shown that k-exponential eventually regular semigroups are necessarily epigroups. 相似文献
20.
Theodore G. Faticoni 《代数通讯》2013,41(1):451-464
In this paper we present a division theorem for the pseudovariety of semigroups OP generated by all semigroups of orientation preserving full transformations on a finite chain, which is achieved by using a natural representation of a certain monoid of transformations of a set X as a monoid of transformations of a subset of X. 相似文献