Boolean Topological Distributive Lattices and Canonical Extensions

This paper presents a unified account of a number of dual category equivalences of relevance to the theory of canonical extensions of distributive lattices. Each of the categories involved is generated by an object having a two-element underlying set; additional structure may be algebraic (lattice or complete lattice operations) or relational (order) and, in either case, topology may or may not be included. Among the dualities considered is that due to B. Banaschewski between the categories of Boolean topological bounded distributive lattices and the category of ordered sets. By combining these dualities we obtain new insights into canonical extensions of distributive lattices. The second author was supported by Slovak grants VEGA 1/3026/06 and APVV-51-009605.     

Distributive Envelopes and Topological Duality for Lattices via Canonical Extensions

We establish a topological duality for bounded lattices. The two main features of our duality are that it generalizes Stone duality for bounded distributive lattices, and that the morphisms on either side are not the standard ones. A positive consequence of the choice of morphisms is that those on the topological side are functional. Towards obtaining the topological duality, we develop a universal construction which associates to an arbitrary lattice two distributive lattice envelopes with a Galois connection between them. This is a modification of a construction of the injective hull of a semilattice by Bruns and Lakser, adjusting their concept of ‘admissibility’ to the finitary case. Finally, we show that the dual spaces of the distributive envelopes of a lattice coincide with completions of quasi-uniform spaces naturally associated with the lattice, thus giving a precise spatial meaning to the distributive envelopes.     

Canonical Extensions and Profinite Completions of Semilattices and Lattices

Canonical extensions of (bounded) lattices have been extensively studied, and the basic existence and uniqueness theorems for these have been extended to general posets. This paper focuses on the intermediate class \({{\boldsymbol{\mathcal{S}}}}_{\wedge}\) of (unital) meet semilattices. Any \({\mathbf S}\in {{\boldsymbol{\mathcal{S}}}}_{\wedge}\) embeds into the algebraic closure system Filt(Filt(S)). This iterated filter completion, denoted Filt²(S), is a compact and \({\textstyle{\bigvee}\,}{\textstyle{\bigwedge}\,}\) -dense extension of S. The complete meet-subsemilattice S ^δ of Filt²(S) consisting of those elements which satisfy the condition of \({\textstyle{\bigwedge}\,}{\textstyle{\bigvee}\,}\) -density is shown to provide a realisation of the canonical extension of S. The easy validation of the construction is independent of the theory of Galois connections. Canonical extensions of bounded lattices are brought within this framework by considering semilattice reducts. Any S in \({{\boldsymbol{\mathcal{S}}}}_{\wedge}\) has a profinite completion, \({\rm Pro}_{{{\boldsymbol{\mathcal{S}}}}_{\wedge}}({\mathbf S})\) . Via the duality theory available for semilattices, \({\rm Pro}_{{{\boldsymbol{\mathcal{S}}}}_{\wedge}}({\mathbf S})\) can be identified with Filt²(S), or, if an abstract approach is adopted, with \({\mathbb F_{\sqcup}}({\mathbb F_{\sqcap}}({\mathbf S}))\) , the free join completion of the free meet completion of S. Lifting of semilattice morphisms can be considered in any of these settings. This leads, inter alia, to a very transparent proof that a homomorphism between bounded lattices lifts to a complete lattice homomorphism between the canonical extensions. Finally, we demonstrate, with examples, that the profinite completion of S, for \({\mathbf S} \in {{\boldsymbol{\mathcal{S}}}}_{\wedge}\) , need not be a canonical extension. This contrasts with the situation for the variety of bounded distributive lattices, within which profinite completion and canonical extension coincide.     

Monadic Bounded Residuated Lattices

Bounded integral residuated lattices form a large class of algebras which contains algebraic counterparts of several propositional logics behind many-valued reasoning and intuitionistic logic. In the paper we introduce and investigate monadic bounded integral residuated lattices which can be taken as a generalization of algebraic models of the predicate calculi of those logics in which only a single variable occurs.     

有界格上三角子模的一种新的延拓方法

介绍了有界格上￡-子模(余子模)的一种新的延拓方法,同时研究了延拓得到的t-子模(余子模)的一些性质.所得的结果表明这种新的延拓方法是一种好的延拓方法.     

Proper Congruence-Preserving Extensions of Lattices

We prove that every lattice with more than one element has a proper congruence-preserving extension.     

Canonical Extensions of Hermitian Operators

The concept of canonical extensions of Hermitian operators is introduced. Not only are such extensions of interest on their own merits, but they also have significant applications (Theorem 3 in particular) in constructing spaces of boundary values of Hermitian operators with various defect numbers. In recent years boundary-value spaces have found important applications in the study of various classes of extensions of Hermitian operators and in scattering theory.     

有界格上的一些函数与几个半群

在有界格上引进了6个函数(算子),研究了它们之间的关系,并且得到了几个半群．     

完全分配格上的全有界一致结构与邻近结构

本文的目的是在具有逆序对合对应的完全分配格上研究点式（拟）一致结构与（拟）邻近中构的联系,证明了在全有界点式一致结构与邻近结构间存在一个一一对应关系。     

Bounded Variation and Tensor Products of Banach Lattices

We introduce bilinear maps of order bounded variation, semivariation and norm bounded variation. We use these notions to extend the knowledge of the projective tensor product of Banach lattices.     

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.     

Integer Programming with Bounded Variables via Canonical Separation

This paper presents a new algorithm for integer programming with bounded variables which is efficient when m < n and when the upper bounds on the variables are small. The main idea is the application of the Balas and Jeroslow canonical hyperplanes and the systematic search of integer points over certain faces of the feasible region. During each iteration the integer points on a certain face are examined, and then this whole face is discarded from the feasible region of a linear programming problem. After a bounded number of iterations, the optimal integer solution is found, if one exists.     

Interval Reductions and Extensions of Orders: Bijections to Chains in Lattices

We discuss bijections that relate families of chains in lattices associated to an order P and families of interval orders defined on the ground set of P. Two bijections of this type have been known:(1) The bijection between maximal chains in the antichain lattice A(P) and the linear extensions of P.(2) The bijection between maximal chains in the lattice of maximal antichains A_M(P) and minimal interval extensions of P.We discuss two approaches to associate interval orders with chains in A(P). This leads to new bijections generalizing Bijections 1 and 2. As a consequence, we characterize the chains corresponding to weak-order extensions and minimal weak-order extensions of P.Seeking for a way of representing interval reductions of P by chains we came upon the separation lattice S(P). Chains in this lattice encode an interesting subclass of interval reductions of P. Let S_M(P) be the lattice of maximal separations in the separation lattice. Restricted to maximal separations, the above bijection specializes to a bijection which nicely complements 1 and 2.(3) A bijection between maximal chains in the lattice of maximal separations S_M(P) and minimal interval reductions of P.     

On Generalized Friedrichs and Krein‐von Neumann Extensions and Canonical Systems

Let S be a densely defined and closed symmetric relation in a Hilbert space ℋ︁ with defect numbers (1,1), and let A be some of its canonical selfadjoint extensions. According to Krein's formula, to S and A corresponds a so‐called Q‐function from the Nevanlinna class N . In this note we show to which subclasses N _γ of N the Q‐functions corresponding to S and its canonical selfadjoint extensions belong and specify the Q‐functions of the generalized Friedrichs and Krein‐von Neumann extensions. A result of L. de Branges implies that to each function Q ∈ N there corresponds a unique Hamiltonian H such that Q is the Titchmarsh‐Weyl coefficient of the two‐dimensional canonical system J_y′ = —zHy on [0, ∞) where Weyl's limit point case prevails at ∞. Then the boundary condition y(0) = 0 corresponds to a symmetric relation T_min with defect numbers (1,1) in the Hilbert space L²_H, and Q is equal to the Q‐function with respect to the extension corresponding to the boundary condition y₁(0) = 0. If H satisfies some growth conditions at 0 or ∞, wepresent results on the corresponding Q‐functions and show under which conditions the generalized Friedrichs or Krein‐von Neumann extension exists.     

半连续格上的一个注记

就文献[3]中的命题4．7提供了一种简单证法。此外,我们给出了在半连续格条件下伪素元的内部刻画。最后,我们定义了一种新的元素——弱素元,给出了伪素元,〈=-素元与弱素元等价的条件。     

格上点式仿紧性

本文在拓扑分子格（ＴＭＬ）上提出一种仿紧性，它以格上点式紧性［３］为特款，讨论了它在ＴＭＬ上的几种不同的表现形式以及它与正规性的关系．