强忠实右S—系

本文引入了相对平坦左Ｓ－系的概念，用来给出了强忠实右Ｓ－系的特征刻划。     

强忠实右S－系

本文引入了相对平坦左Ｓ－系的概念，用来给出了强忠实右Ｓ－系的特征刻划。     

L—逆左系对幺半群的刻画

正则左Ｓ－系是ｖｏｎ ｎｅｕｍａｎｎ正则半群的自然推广，逆左Ｓ－系是逆半群的自然扩广，作为左逆半群的自然推广，本文引入了Ｌ－逆左系的概念，并用来刻画了几类幺半群，如左逆幺半群，逆幺半群，ａｄｅｑｕａｔｅ幺半群等。     

所有循环平坦系满足条件（P）的PSF幺半群

本文讨论所有循环平坦系满足条件（Ｐ）的幺半群的“元素－－理想”特征问题,该问题至今仍未获解决,在Ｓ是左ＰＳＦ幺半群的条件下,本文证明了所有循环平坦右Ｓ－系满足条件（Ｐ）当且仅当Ｓ的任意元ｘ或者是右可消元,或者是右零元,当且仅当对Ｓ的任意真右理想Ｉ,或存在ａ∈Ｉ－Ｉａ,或Ｉ中的所有元素均为右零元,该结果改进并推广了「４」、「７」、「８」、「１５」中的部分结果。     

L－逆左系对幺半群的刻画

正则左Ｓ-系是ｖｏｎ Ｎｅｕｍａｎｎ正则半群的自然推广，逆左Ｓ-系是逆半群的自然推广．作为左逆半群的自然推广，本文引入了Ｌ-逆左系的概念，并用来刻画了几类幺半群，如左逆幺半群，逆幺半群，ａｄｅｑｕａｔｅ幺半群等．     

关于所有强平坦右S-系是正则系的幺半群(英)

本论文考虑了所有强平坦右S-系是正则系的幺半群的刻画,证明了所有强平坦右S-系是正则S-系当且仅当S是右PSF幺半群并且S的每一个左coilpasible子幺半群包含左零元．该结果对Kilp和Knauer在文献[7]中的问题给出了一个新的回答．     

关于S—系统的纯性

设Ｓ是幺半群，在右Ｓ－系范畴Ａｃｔ－Ｓ中，有两种纯性的概念，分别被Ｎｏｒｍａｋ，Ｇｏｕｌｄ和Ｒｅｎｓｈａｗ所研究。我们分别称之为ＮＧ－纯性和Ｒ－纯性，本文考虑ＮＧ－纯性和Ｒ－纯性的关系。我们证明了ＮＧ－纯性蕴含Ｒ－纯性，并且给出例子说明反过来是不对的，最后我们引入了关系正合序列的概念，并用来研究循环系的Ｒ－纯循环子系的性质。     

关于S－系的纯性

设Ｓ是么半群，在右Ｓ－系范畴Ａｃｔ－Ｓ中，有两种纯性的概念，分别被Ｎｏｒｍａｋ，Ｇｏｕｌｄ和Ｒｅｎｓｈａｗ所研究．我们分别称之为ＮＧ－纯性和Ｒ－纯性．本文考虑ＮＧ－纯性和Ｒ－纯性的关系．我们证明了ＮＧ－纯性蕴含Ｒ－纯性，并且给出例子说明反过来是不对的．最后我们引入了关系正合序列的概念，并用来研究循环系的Ｒ－纯循环子系的性质．     

极大本质左理想是理想的SF－环

由Ｒａｍａｍｕｒｔｈｉ和Ｍｉｎｇ的两个公开问题所推动，本文证明了如下结果：（１）如果Ｒ是ＭＥＬＴ，ＳＦ－环，那么Ｒ是正则环；（２）如果Ｒ是ＭＥＬＴ，左ＣＥ－内射，右ＳＦ－环，那么Ｒ是具有有界指数的左和右自内射正则，左和右Ｖ－环．这就给出了Ｒａｍａｍｕｒｔｈｉ和Ｍｉｎｇ两个公开问题的部分回答．     

关于McCoy定理

关于ＭｃＣｏｙ定理章聚乐，杜先能（安徽师范大学数学系，芜湖）关键词素理想，ｍ－系，＊－素子模，对偶模．分类号＾。Ｓ（１９９１）１６Ｄ３。／ｃＣ。。１５３．３本文中，Ｒ表示有单位元的结合环，Ｍ表示左Ｒ一模，并且Ｍ的对偶模Ｈｏｒｎ。（Ｍ，Ｒ）记为Ｍ”．模...     

C(P)系对幺半群的刻画

设S是幺半群.本文介绍并研究了正则右系的一个推广.一个右S-系A称为C(P)系,如果A的所有循环子系满足条件(P).本文证明了右C(P)系形成了右S-系的一个新的类,同时,C(P)性质为幺半群同调分类研究提供了新思路.     

Principal Weak Flatness and Regularity of Diagonal Acts

For a monoid S, the set S × S equipped with the componentwise right S-action is called the diagonal act of S and is denoted by D(S). A monoid S is a left PP (left PSF) monoid if every principal left ideal of S is projective (strongly flat). We shall call a monoid S left P(P) if all principal left ideals of S satisfy condition (P). We shall call a monoid S weakly left P(P) monoid if the equalities as = bs, xb = yb in S imply the existence of r ∈ S such that xar = yar, rs = s. In this article, we prove that a monoid S is left PSF if and only if S is (weakly) left P(P) and D(S) is principally weakly flat. We provide examples showing that the implications left PSF ? left P(P) ? weakly left P(P) are strict. Finally, we investigate regularity of diagonal acts D(S), and we prove that for a right PP monoid S the diagonal act D(S) is regular if and only if every finite product of regular acts is regular. Furthermore, we prove that for a full transformation monoid S = 𝒯 _X , D(S) is regular.     

一类循环系的平坦性

设Ｓ是幺半群,ｘ_１,ｘ₂,…∈Ｓ且满足ｘ_i+１ｘ_i＝ｘ_i,ｉ＝１,２……ｙ是S中的任意元素,记H={(yx_i,x_i)|i=1,2,…}.设ρ(H)是S的由Ｈ生成的最小右同余,本文证明了S／ρ（Ｈ）是平坦右Ｓ－系．     

Amenability of semigroups and the Ore condition for semigroup rings

Semigroup Forum - It is known that if a cancellative monoid M is left amenable then the monoid ring K[M] satisfies the Ore condition, that is, there exist nontrivial common right multiples for the...     

A partial converse to a theorem of Tamari

Let M be a cancellative monoid such that the monoid ring ℤM has no zero divisors. We show that if the monoid consisting of all elements of ℤM with strictly positive coefficients has nonzero common right multiples, then M is left amenable.     

Endomorphism monoids of free acts and O-wreath products of monoids

Monoids and acts which may have zero elements are considered. In Section 1 we construct a O-wreath product of monoids. In 2 we prove the theorem that the endomorphism monoid of a free act over a monoid with zero can be represented as a O-wreath product. Considering monoids with tero we are interested in their annihilator properties. In 3 we give necessary and sufficient conditions for a O-wreath product of monoids to be a right (left) Baer (Rickart) monoid. In 4 we obtain as a consequence corresponding conditions for the endomorphism monoid of a free act over a monoid with zero.     

右消去幺半群、左正则带和左正则型A幺半群

本文利用右消去幺半群,左正则带建立了真左正则型A幺半群．在证明了任一左正则型A幺半群均有P－覆盖后,给出P－覆盖的结构．     

PERFECT rpp SEMIGROUPS

The aim of this paper is to study a class of rpp semigroups, namely the perfect rpp semigroups. We obtain some characterization theorems for such semigroups. In particular, the spined product structure of perfect rpp semigroups is established. As an application of spined product structure, we prove that a perfect rpp semigroup is a strong semilattice of left cancellative planks. By a left cancellative plank, we mean a product of a left cancellative monoid and a rectangular band. Thus, the work of J.B. Fountain on C-rpp semigroups is further developed.

     

Hereditary endomorphism monoids of projective acts

Projective acts whose endomorphism monoids are left or right (semi-) hereditary are characterized. For example, it is shown that for a noncyclic free or projective S-act P, End P is left (semi) hereditary if and only if P ≈ Se₁ Π Se₂ and e₁Se₁, e₂Se₂ are groups.