偏序集代数的同构问题

在[1]中对局部有限偏序集I={I,≤}及域K引入了关联代数KI的概念.这里的“局部有限”是指对任意a,b∈I,a≤b,集合{x∈I|a≤x≤b}.是有限集.KI的定义是:其元素是域K上以I中元素为行与列的足码的形式矩阵(кa,b)a,b∈I,(即允许有无限多个ka,b≠0)且满足条件:当a≮b时有ka,b=0.注意到I的局部有限性,易知上述形式矩阵的全体关于通常矩阵的加法和乘法以及数乘作成域K上的一个结合代数,称之为I在K上的关联代数KI。     

R(L$型诱导空间的分离性和良紧性

In this paper, we prove that （L^X,5） is T0,T1, T2, regular （T3）, normal （T4） and completely regular spaces if and only if （R（L）^X, ω（δ）） is T0, T1, T2, regular （T3）, normal （T4） and completely regular spaces, respectively, and （L^X,δ） is N-compact if and only if （R（L）^X, ω（δ）） is N-compact.     

［X→L］上的Isbell拓扑和Scott拓扑

本文证明了：对ｃｏｒｅｃｏｍｐａｃｔ空间Ｘ和具有最小元的有界完备连续ＤＣＰＯＬ，［Ｘ→Ｌ］上的Ｉｓｂｅｌｌ拓扑与Ｓｃｏｔｔ拓扑重合．并且构造两个反例说明：若Ｌ不具有最小元，或Ｌ具有最小元但不满足有界完备性，则［Ｘ→Ｌ］上的Ｉｓｂｅｌｌ拓扑与Ｓｃｏｔｔ拓扑不必重合．     

偏序集的关联环的同构问题

设Ｘ是局部有限偏序集（或拟序集），Ｒ是含１的结合环，Ⅰ（Ｘ，Ｒ）是Ｒ上Ｘ的关联环，关联环的同构问题是指：问题１：怎样的环，能使环同构Ⅰ（Ｘ，Ｒ）Ⅰ（Ｘ，Ｒ）推出偏序集之间的同构Ｘ芒Ｘ’？问题２：怎样的环或偏序集，能使环同构Ⅰ（Ｘ，Ｒ）Ⅰ（Ｘ，Ｓ）推出Ｒ　Ｓ？本文证明了对唯一幂等元环（非交换），问题１有正面回答；对问题２，我们证明了对交换不可分解环Ｒ、Ｓ，由环同构Ⅰ（Ｘ，Ｒ）Ⅰ（Ｘ，Ｒ）可得到Ｒ＝Ｓ，Ｘ＝Ｘ’。     

Z/(pr)上模p上三角矩阵的轨道

本文证明了由Birkhoff给出的有限Abel p-群的子群的标准矩阵表示所构造的从Z/pkZ×...×/pk的子群格到多重集{1k,2k,...,nk}(n3)的子集格之间的保秩保序映射ψ,在集中每一点的原象集均是Z/pk上的一般线性群的子群--模p上三角矩阵群的轨道.这个结果当k退化为1时,便可得到Knuth构造的关于子空间格到子集格的保秩保序映射也具有这种性质.     

Rasche方法在偏序集上最优集止问题中的应用

本用Ｒａｓｃｈｅ方法对偏序集Ｓ中的点进行了筛选，筛选算法简单明了。设Ｂ（Ｅ）记筛选后的点集，我们证明了１）Ｖ＝ｓｕｐ ＥＸｒ＝ｓｕｐ｛ＥＸτ：τ∈Ｂ（Ｅ）｝；２）若最优停点存在，则必几乎处处取值于Ｂ（Ｅ）中。     

关于强稠密语言与G.R.T-问题的一个等价陈述

在本文中,我们推广了[2]中相关对的概念,从而导出强稠密语言的概念,利用强稠密语言作为桥梁,我们给出了[1]中一个公开问题——G.R.T.-问题的一个等价陈述,同时也部分地回答了该问题.     

测度拓扑和连续偏序集的刻画

研究偏序集上的测度拓扑以及与其它内蕴拓扑间的关系,利用测度拓扑刻画了偏序集的连续性.构造了反例说明存在完全分配格,其上的测度拓扑不是连续格从而不是局部紧拓扑.     

Strengthened fixed point property and products in ordered sets

Strengthened fixed point property for ordered sets is formulated. It is weaker than the strong fixed point property due to Duffus and Sauer and stronger than the product property meaning that A × Y has the fixed point property whenever A has the former and Y has the latter. In particular, doubly chain complete ordered sets with no infinite antichain have the strengthened fixed point property whenever they have the fixed point property, which yields a transparent proof of the well-known theorem saying that doubly chain complete ordered sets with no infinite antichain have the product property whenever they have the fixed point property. The new proof does not require the axiom of choice. Presented at the Summer School on General Algebra and Ordered Sets, Malá Morávka, 4–10 September 2005.     

Strictly Order-Preserving Maps into Z, II. A 1979 Problem of Erné

A lattice L is constructed with the property that every interval has finite height, but there exists no strictly order-preserving map from L to Z. A 1979 problem of Erné (posed at the 1981 Banff Conference on Ordered Sets) is thus solved. It is also shown that if a poset P has no uncountable antichains, then it admits a strictly order-preserving map into Z if and only if every interval has finite height.     

Existence and Uniqueness of Fixed Point in Partially Ordered Sets and Applications to Ordinary Differential Equations

We prove some fixed point theorems in partially ordered sets, providing an extension of the Banach contractive mapping theorem. Having studied previously the nondecreasing case, we consider in this paper nonincreasing mappings as well as non monotone mappings. We also present some applications to first–order ordinary differential equations with periodic boundary conditions, proving the existence of a unique solution admitting the existence of a lower solution. Research partially supported by Ministerio de Educación y Ciencia and FEDER, Project MTM2004-06652-C03-01, and by Xunta de Galicia and FEDER, Projects PGIDIT02PXIC20703PN and PGIDIT05PXIC20702PN     

The Fixed Point Property for Posets of Small Width

The fixed point property for finite posets of width 3 and 4 is studied in terms of forbidden retracts. The ranked forbidden retracts for width 3 and 4 are determined explicitly. The ranked forbidden retracts for the width 3 case that are linearly indecomposable are examined to see which are minimal automorphic. Part of a problem of Niederle from 1989 is thus solved.     

半序度量空间中公共二元随机重合点定理及其应用

在完备可分的半序度量空间中,引入了随机映射对(F,G)关于g随机半序弱增以及(F,G)随机半序弱增的定义,研究了在满足一定非线性压缩条件下的随机映射列F_k:Ω×X×X→X,k=1,2…,g:Ω×X→X和h:Ω×X→X的公共二元随机重合点与公共二元随机不动点问题,所得结果推广了已有文献中的一些不动点定理.     

Contractive Mapping Theorems in Partially Ordered Sets and Applications to Ordinary Differential Equations

We prove the existence and uniqueness of solution for a first-order ordinary differential equation with periodic boundary conditions admitting only the existence of a lower solution. To this aim, we prove an appropriate fixed point theorem in partially ordered sets. ★ Partially supported by Ministerio de Ciencia y Tecnología/ FEDER, project BFM2001-3884-C02-01; and by Xunta de Galicia/ FEDER, project PGIDIT02PXIC20703PN.     

概率赋范空间上的一些不动点定理的进一步分析

该文在局部有界ＰＮ空间或邻域卜局部凸ＰＮ空间上,证明了非空完备子集上的概率压缩映象必有唯一不动点;并在度量线性空间中给出了关于伪范族一致压缩映象的不动点定理．     

关于M-R公开问题的注记

在本文中,通过关联ＢＣＫ-代数与立体格公理系统的联系,给出了Ｍ-Ｒ公开问题一个肯定的答复．     

Shellability of Interval Orders

An finite interval order is a partially ordered set whose elements are in correspondence with a finite set of intervals in the line, with disjoint intervals being ordered by their relative position. We show that any such order is shellable in the sense that its (not necessarily pure) order complex is shellable.