半极小集及其应用

在完备格中,引入半极小集概念,得到完备格L是半连续格当且仅当每一个元都有半极小集这一结论,同时给出半极小集的一些刻画性质.在半Scott连续映射的帮助下,给出了保半极小集的一些映射性质,并用这些性质证明了半连续格的子半格、商半格还是半连续格.     

相似剩余格及其对应逻辑系统的完备性

引入了相似剩余格的概念,讨论了剩余格上相似算子和等价算子的关系,并得到了真值剩余格和相似剩余格相互转化的方法.其次,研究了相似剩余格上的相似滤子,利用相似滤子刻画了可表示的相似剩余格.最后,引入了相似剩余格对应的逻辑系统,证明了其完备性定理,并得到了其成为半线性逻辑的条件.     

完备主因子格

本文引入了主因子格的概念,讨论了完备主因子格中元素的结构.得到了完备主因子分配格有不可约并既分解的一个充要条件,证明了完备下连续的主因子格是有不可约并既分解的.最后讨论了完备主因子格中不可约并既分解的惟一性及可替换性,得到了完备下连续的主因子格有惟一不可约并既分解或者有可替换不可约并既分解的一些充要条件.     

完备模格的有限条件

本文研究完备模格的有限条件,给出了完备模格是Artin(Noether)格的若干等价条件,得到了完备模格中元1分解为有限个独立原子并的等价刻画,证明了上连续完备半单模格中元1的任意两个独立原子分解具有相同的基数.     

关于格的极小生成元集

本文证明了格的极小生成元集一定是最小生成元集且只能是非零完全并既约元全体，证明了分配格具有最小生成元集的必要条件是它满足并无限分配律．本文还证明了完全Ｈｅｙｔｉｎｇ代数具有最小生成元集当且仅当它是强代数格，证明了完备格是强代数格当且仅当它和它的对偶格均是具有最小生成元集的分配格．     

半连续格的半素极小集与序同态扩张

对完备格引入半素极小集的概念,证明完备格L为半连续格当且仅当L中的每个元在L中存在半素极小集,给出半连续格的两个序同态扩张定理.     

分子格范畴中的极限

本文通过对完备格上“”关系的抽象分析，引入了　完备格及　下集的概念。讨论了下集的一系列性质。证明了一个完备格中所有下集之集构成一个分子格，由此再结合范畴论知识，构造出了分子格范畴中的极限结构。解决了分子格范畴性质这一研究领域中最困难的问题之一。     

ψ—连续格的刻划与完全分配格的拓扑表示定理

本文在完备格中引入ψ－Ｓ集的概念，并在讨论ψ－Ｓ集族性质的基础上给出－ψ－连续格的一族拓扑及格论刻划，用局部超紧的Ｓｏｂｅｒ空间范畴给出完全分配格的拓扑表示定理。     

无限格与其非标准扩张

在非标准κ-饱和模型下,研究了无限格L的非标准扩张*L的性质及其在L-集滤子理论中的应用.首先,定义了κ-完备格的概念,讨论了完备格与κ-完备格之间的关系,证明了无限格L的非标准扩张*L是κ-完备格.其次,定义了L-集滤子的单子,利用κ-完备格证明了此定义是合理的.最后,利用L-集滤子的单子给出了L-集滤子族上确界存在的充分且必要条件.     

软代数的自然表示

指出了软代数现行表示的非自然性;通过引入新的集对F格与伪幂集格,获得了两个自然的软代数表示定理,并证明了它们在某种意义上不可能再改进.     

A constructive approach to the finite congruence lattice representation problem

A finite lattice is representable if it is isomorphic to the congruence lattice of a finite algebra. In this paper, we develop methods by which we can construct new representable lattices from known ones. The techniques we employ are sufficient to show that every finite lattice which contains no three element antichains is representable. We then show that if an order polynomially complete lattice is representable then so is every one of its diagonal subdirect powers. Received August 30, 1999; accepted in final form November 29, 1999.     

On coatoms in lattices of quasivarieties of algebraic systems

It is found the necessary condition for the lattice of quasivarieties has a finite set of coatoms. In particular if a quasivariety is generated by a finitely generated abelian-by-polycyclic-by-finite group or a totally ordered group then it has a finite set of proper maximal subquasivarieties. Also it is proved that the set of quasiverbal congruence relations of a finitely defined universal algebra is closed under any meets. Received March 23, 1999; accepted in final form June 7, 1999.     

Collection of Finite Lattices Generated by a Poset

It is proved that the collection of all finite lattices with the same partially ordered set of meet-irreducible elements can be ordered in a natural way so that the obtained poset is a lattice. Necessary and sufficient conditions under which this lattice is Boolean, distributive and modular are given.     

The Lattice of Completions of an Ordered Set

For any ordered set P, the join dense completions of P form a complete lattice K(P) with least element O(P), the lattice of order ideals of P, and greatest element M(P), the Dedekind–MacNeille completion P. The lattice K(P) is isomorphic to an ideal of the lattice of all closure operators on the lattice O(P). Thus it inherits some local structural properties which hold in the lattice of closure operators on any complete lattice. In particular, if K(P) is finite, then it is an upper semimodular lattice and an upper bounded homomorphic image of a free lattice, and hence meet semidistributive.     

效应代数的表示

本文讨论了抽象效应代数的表示问题. 对于一个抽象效应代数(E,⊕, 0, 1), 如果存在一个Hilbert 空间 H 和一个单态射 φ:E →ε(H), 那么称 E 为可表示的且称(φ,H) 是E 的一个表示, 其中ε(H) 表示 H 上所有正压缩算子构成的效应代数. 给出了一些可表示的和不可表示的效应代数的例子, 证 明了非空集 X 上的任一模糊集系统 F 和Boolean 代数B_X 都是可表示的效应代数.     

并素元有限生成格的弱直积分解

本文建立了并素元有限生成格的弱直积分解,并给出一个解决并素元生成的完全Heyting代数的直积分解问题的新方法;作为弱直积分解的应用,证明了并素元有限生成的完全Heyting代数必然同构于有限个既约的完全Heyting代数的直积,证明了并素元有限生成格是Boole代数的充要条件是它同构于某有限集的幂集格.     

Going down in (semi)lattices of finite moore families and convex geometries

In this paper we first study what changes occur in the posets of irreducible elements when one goes from an arbitrary Moore family (respectively, a convex geometry) to one of its lower covers in the lattice of all Moore families (respectively, in the semilattice of all convex geometries) defined on a finite set. Then we study the set of all convex geometries which have the same poset of join-irreducible elements. We show that this set—ordered by set inclusion—is a ranked join-semilattice and we characterize its cover relation. We prove that the lattice of all ideals of a given poset P is the only convex geometry having a poset of join-irreducible elements isomorphic to P if and only if the width of P is less than 3. Finally, we give an algorithm for computing all convex geometries having the same poset of join-irreducible elements.      

A representation theorem for measurable relation algebras

A relation algebra is called measurable when its identity is the sum of measurable atoms, where an atom is called measurable if its square is the sum of functional elements.In this paper we show that atomic measurable relation algebras have rather strong structural properties: they are constructed from systems of groups, coordinated systems of isomorphisms between quotients of the groups, and systems of cosets that are used to “shift” the operation of relative multiplication. An atomic and complete measurable relation algebra is completely representable if and only if there is a stronger coordination between these isomorphisms induced by a scaffold (the shifting cosets are not needed in this case). We also prove that a measurable relation algebra in which the associated groups are all finite is atomic.