奇异变换半群Sing_n的非群平方幂等元秩

设Sing_n是[n]上的奇异变换半群.证明了半群Sing_n是由秩为n-1的非群平方幂等元生成的,且它的非群平方幂等元秩为(n(n-1))/2.     

半群ASn的秩

设A_n和Sing_n分别是X_n上的交错群和奇异变换半群.考虑变换半群AS_n=A_n∪Sing_n,证明了变换半群AS_n的秩为3.     

Generating Sets of Finite Transformation Semigroups PK(n,r) and K (n,r)

Let P _n and T _n be the partial transformation and the full transformation semigroups on the set {1,…, n}, respectively. In this paper we find necessary and sufficient conditions for any set of partial transformations of height r in the subsemigroup PK(n, r) = {α ∈P _n : |im (α)| ≤r} of P _n to be a (minimal) generating set of PK(n, r); and similarly, for any set of full transformations of height r in the subsemigroup K(n, r) = {α ∈T _n : |im (α)| ≤r} of T _n to be a (minimal) generating set of K(n, r) for 2 ≤ r ≤ n ? 1.     

奇异变换半群中J类的幂乘数

首先给出奇异变换半群中J类的幂乘数的定义,然后讨论奇异变换半群中J类的幂乘数的性质.     

一类核具有连续横截面变换半群的秩

设X_n={1,2,…,n}并赋予自然数序,MCK_n是X_n上核具有连续横截面保序或反序变换所构成的半群.K_n是MCK_n的最大正则子半群.本文将考虑K_n的理想K(n,r)={α∈K_n:|im(α)|≤r}(3≤r≤n-1).证明了K(n,r)的秩为(n-r+1)(n-r+2)(n-r+3)/6.     

On the Monoid of All Partial Order-Preserving Extensive Transformations

A partial transformation α on an n-element chain X _n is called order-preserving if x ≤ y implies xα ≤yα for all x, y in the domain of α and it is called extensive if x ≤ xα for all x in the domain of α. The set of all partial order-preserving extensive transformations on X _n forms a semiband POE _n . We determine the maximal subsemigroups as well as the maximal subsemibands of POE _n .     

On the Number of Nilpotents in the Partial Symmetric Semigroup

Abstract

In this note, we obtain and discuss formulae for the total number of nilpotent partial and nilpotent partial one–one transformations of a finite set.     

半群PO_(n,r)的秩

设POn为Xn上的保序部分变换半群.对任意的2≤r≤n一1,考虑半群PO_(n,r)={α∈PO_n:Im(α)■[r]}([r]={1,2,…,r}),证明了PO_(n,r)的秩为Σn-1k=r(nk)((k-1)(r-1))+r-1.     

On the Finite Base Property for Semigroup Varieties

No algorithm determines from an arbitrary recursive system of semigroup identities whether the variety defined by this system is finitely based.     

Congruences of a Permutable Inverse Semigroup of Finite Rank

We describe the structure of any congruence of a permutable inverse semigroup of finite rank. __________ Translated from Ukrains'kyi Matematychnyi Zhurnal, Vol. 57, No. 4, pp. 469–473, April, 2005.     

Nonnegative Rank Factorization of a Nonnegative Matrix A with A A ≥0

In this article we obtain a nonnegative rank factorization of nonnegative matrices A satisfying one or both of the following conditions: (i) AA † ≥0 (ii) A † A ≥0, thus providing a new set of conditions that guarantee the existence of a nonnegative least-squares solution of a linear system. Indeed, the characterization of such matrices improves some of the previous known conditions for the existence of a nonnegative least-squares solution of a linear system.     

On the Ranks of Certain Semigroups of Orientation Preserving Transformations

We classify the unmixed squarefree lexsegment ideals and determine those which are Cohen–Macaulay.     

The Full Transformation Semigroups of Finite Rank are Amalgamation Bases for Finite Semigroups

In this article, we prove that the full transformation semigroup on a finite set is an amalgamation base for finite semigroups.     

单调压缩变换半群的秩

设自然数n≥4,X_n={1,2,…,n},MC_n是X_n上的单调压缩全变换半群,证明了MC_n的秩为n-1.     

半群OI_n(k)的秩

设OI_n是[n]上的保序严格部分一一变换半群.对任意1≤k≤n-1,研究半群OI_n(k)={α∈OI_n:(■x∈dom(α))x≤k■xα≤k}的秩,证明了半群OI_n(k)的秩为n+1.     

半群P_n(k)的正则性和Green关系

设P_n是X_n={1,…,n}上的部分变换半群.对任意1≤k≤n,令P_n(k)={α∈P_n:(x∈dom(α)x≤k■xα≤k},则易验证P_n(k)是P_n的子半群.刻画了半群P_n(k)的正则元的特征,并且描述了这个半群上的Green关系.     

Factorisable Semigroups of Generalized Transformations

ABSTRACT

If X and Y are sets, we let P(X, Y ) denote the set of all partial transformations from X into Y (that is, all mappings whose domain and range are subsets of X and Y, respectively). We define an operation * on P(X, Y ) by choosing θ ∈ P(Y, X) and writing: α*β = α °θ°β, for each α, β ∈ P(X, Y ). Then (P(X, Y ), *) is a semigroup, and some authors have determined when this is regular (Magill and Subbiah, 1975 Magill , K. D. , Jr. Subbiah , S. ( 1975 ). Green's relations for regular elements of sandwich semigroups. I. General results . Proc. London Math. Soc. 31 : 194 – 210 . [CSA] [Crossref], [Web of Science ®] , [Google Scholar]), when it contains a “proper dense subsemigroup” (Wasanawichit and Kemprasit, 2002 Wasanawichit , A. , Kemprasit , Y. ( 2002 ). Dense subsemigroups of generalized transformation semigroups . J. Austral. Math. Soc. 73 ( 3 ): 433 – 445 . [CSA] [Crossref] , [Google Scholar]) and when it is factorisable (Saengsura, 2001 Saengsura , K. ( 2001 ). Factorizable on (P(X, Y ), θ) , MSc thesis, 23 pp (in Thai, with English summary), Department of Mathematics, Khon Kaen University, Khon Kaen, Thailand, 2001.  [Google Scholar]). In this paper, we extend the latter work to certain subsemigroups of (P(X, Y ), *). We also consider the corresponding idea for partial linear transformations from one vector space into another. In this way, we generalise known results for total transformations and for injective partial transformations between sets, and we establish new results for linear transformations between vector spaces.     

半群OCK_n的理想的极大子半群

设X_n={1,2,…,n}并赋予自然数序,OCK_n是X_n上的具有核连续的保序变换半群.将考虑OCK_n的理想OCK(n,r)={α∈OCK_n:|imα|≤r}(3≤r≤n-1),并得到了OCK(n,r)的极大子半群的完全分类.