Cartesian closed categories of FƵ-domains

A subset system Z assigns to each partially ordered set P a certain collection Z（P） of subsets. In this paper, a new kind of subset systems called directable subset systems is introduced. For a directable subset system Z, the concepts of FZ-way-below relation and FZ-domain are introduced. The well-known Scott topology is naturally generalized to the Z-level and the resulting topology is called FZ-Scott topology, and the continuous functions with respect to this topology are characterized by preserving the suprema of directed Z-sets. Then, we mainly consider a generalization of the cartesian closedness of the categories DCPO of directed complete posets, BF of bifinite domains and FS of FS-domains to the Z-level. Corresponding to them, it is proved that, for a suitable subset system Z, the categories FZCPO of Z-complete posets, FSFZ of finitely separated FZ-domains and BFFZ of bifinite FZ-domains are all cartesian closed. Some examples of these categories are given.     

Z-Continuous Posets and Their Topological Manifestation

A subset selection Z assigns to each partially ordered set P a certain collection Z P of subsets. The theory of topological and of algebraic (i.e. finitary) closure spaces extends to the general Z-level, by replacing finite or directed sets, respectively, with arbitrary Z-sets. This leads to a theory of Z-union completeness, Z-arity, Z-soberness etc. Order-theoretical notions such as complete distributivity and continuity of lattices or posets extend to the general Z-setting as well. For example, we characterize Z-distributive posets and Z-continuous posets by certain homomorphism properties and adjunctions. It turns out that for arbitrary subset selections Z, a poset P is strongly Z-continuous iff its Z-join ideal completion Z P is Z-ary and completely distributive. Using that characterization, we show that the category of strongly Z-continuous posets (with interpolation) is concretely isomorphic to the category of Z-ary Z-complete core spaces. For suitable subset selections Y and Z, these are precisely the Y-sober core spaces.     

Rudin性质与拟Z-连续Domain

对一般子集系统 Z,引入了 Rudin性质,给出了它的映射式刻划,作为拟连续偏序集和Z-连续偏序集的公共推广,引入了拟Z-连续Domain的概念,讨论了拟Z-连续Domain的基本性质,特别地,给出了 Rudin性质及其映射式刻划在拟 Z-连续Domain方面的若干应用,将关于拟连续偏序集的主要结果推广至了拟 Z-连续 Domain情形。     

Quasicontinuity of Posets via Scott Topology and Sobrification

In this paper, posets which may not be dcpos are considered. In terms of the Scott topology on posets, the new concept of quasicontinuous posets is introduced. Some properties and characterizations of quasicontinuous posets are examined. The main results are: (1) a poset is quasicontinuous iff the lattice of all Scott open sets is a hypercontinuous lattice; (2) the directed completions of quasicontinuous posets are quasicontinuous domains; (3) A poset is continuous iff it is quasicontinuous and meet continuous, generalizing the relevant result for dcpos. Supported by the NSF of China (10371106, 10410638) and by the Fund (S0667-082) from Nanjing University of Aeronautics and Astronautics.     

拟Z-连续domain和Z-交连续domain

对一般子集系统Z,引入了Rudin性质、拟Z-连续domain及Z-交连续 domain的概念,讨论了它们的基本性质.特别是Z-连续性、拟Z-连续性、 Z-交连 续性和Z-Lawson拓扑之T2性之间的相互关系. 证明了当子集系统Z满足一定条件 时,拟Z-连续domain P上的Z-way below关系Z具有插入性质, P上的Z-Lawson 拓扑λZ(P)是T2的,且P可用Z-Lawson同态嵌入到某方体之中.文中给出了一个 domain P,其上的Lawson拓扑λ(P)是T2的,但P不是拟连续性domain.     

Generalized Continuous Posets and a New Cartesian Closed Category

With every subset selection for posets, there is associated a certain ideal completion . As shown by Erné, such completions help to extend classical results on domains and similar structures in the absence of the required joins. Some results about –predistributive or –precontinuous posets and –continuous functions are summarized and supplemented. In particular, several central results on function spaces in domain theory are extended to the setting of productive closed subset selections. The category FSBP, in which objects are finitely separated and upper bounded posets and arrows are continuous functions between them, is shown to be cartesian closed. This research is supported by the National Natural Science Foundation of China, 10471035.     

Strongly continuous posets and the local Scott topology

In this paper, the concept of strongly continuous posets (SC-posets, for short) is introduced. A new intrinsic topology—the local Scott topology is defined and used to characterize SC-posets and weak monotone convergence spaces. Four notions of continuity on posets are compared in detail and some subtle counterexamples are constructed. Main results are: (1) A poset is an SC-poset iff its local Scott topology is equal to its Scott topology and is completely distributive iff it is a continuous precup; (2) For precups, PI-continuity, LC-continuity, SC-continuity and the usual continuity are equal, whereas they are mutually different for general posets; (3) A T₀-space is an SC-poset equipped with the Scott topology iff the space is a weak monotone convergence space with a completely distributive topology contained in the local Scott topology of the specialization order.     

Cartesian Closed Extensions of Subcategories of CONT

In this paper we give a uniform way of proving cartesian closedness for many new subcategories of continuous posets. We define C-P to be the category of continuous posets whose D–completions are isomorphic to objects from C, where C is a subcategory of the category CONT of domains. The main result is that if C is a cartesian closed full subcategory of ALG _⊥ or BC, then C-P is also a cartesian closed subcategory of the category CONTP of continuous posets and Scott continuous functions. In particular, we have the following cartesian closed categories : BC-P, LAT-P, aL-P, aBC-P, B-P, aLAT-P, ω -B-P, ω -aLAT-P, etc.     

On the continuity of the feasible set in extremally linear problems

The purpose of this paper is to investigate continuity properties of the feasible set in extremally linear problems. Feasible sets of such problems are subsets of Fⁿ (the n-fold cartesian product of a fully ordered group (F,º)) and are described by a finite or an infinite number of inequalities or equalities, which are linear with respect to the operations ? and º. Thereby, the operation ? is induced by the fully-order in F by setting x?y = y iff x ≤ y for x, y in F. In particular, we derive conditions for the upper- and lower-semi-continuity of the feasible-set-mapping Z and investigate the structure of certain parameter sets. Especially, we show that the compactness of the feasible set, resp. the condition that the closure of the set of the strict feasible points is the feasible set, is sufficient for the upper-semi-continuity (u.s.c), resp. the lower-semi-continuity (l.s.c.) of Z, but - unlike to semi-infinite linear optimization - is not necessary for the u.s.c, resp. l.s.c. If we restrict Z on a certain subset of the parameter set, these conditions are also necessary. This paper is a continuation of the author's work in [6] and [7].     

Order topology and bi-Scott topology on a poset

In this paper, some properties of order topology and bi-Scott topology on a poset are obtained. Order-convergence in posets is further studied. Especially, a sufficient and necessary condition for order-convergence to be topological is given for some kind of posets.     

Weak Factorization Systems and Topological Functors

Weak factorization systems, important in homotopy theory, are related to injective objects in comma-categories. Our main result is that full functors and topological functors form a weak factorization system in the category of small categories, and that this is not cofibrantly generated. We also present a weak factorization system on the category of posets which is not cofibrantly generated. No such weak factorization systems were known until recently. This answers an open problem posed by M. Hovey.     

Topologies on products of partially ordered sets II: Ideal topologies

Within the theory of ideals in partially ordered sets, several difficulties set in which do not occur in the special case of lattices (or bidirected posets). For example, a finite product of ideals in the factor posets need not be an ideal in the product poset. The notion ofstrict ideals is introduced in order to remedy some deficiencies occurring in the general case of an arbitrary product of posets. Besides other results, we show the following main theorem: The ideal topology (cf. [2]) of a product of non-trivial posets coincides with the product topology if and only if the number of factors is finite (4.19.). Presented by L. Fuchs     

偏序集上的测度拓扑与稠拓扑

In this paper,the concepts of the essential topology and the density topology of dcpos are generalized to the setting of general posets.Basic properties of the essential topology and relations with other intrinsic topologies are explored.Comparisons between the density topology and the measurement topology are made.Via the essential topology,the density topology and the measurement topology,we obtain properties and characterizations of bases of continuous posets.We also provide some new conditions for a continuous poset to be an algebraic poset.     

Continuity of posets via Scott topology and sobrification

In this paper, posets which may not be dcpos are considered. The concept of embedded bases for posets is introduced. Characterizations of continuity of posets in terms of embedded bases and Scott topology are given. The main results are:

(1)

A poset is continuous iff it is an embedded basis for a dcpo up to an isomorphism;

(2)

A poset is continuous iff its Scott topology is completely distributive;

(3)

A topological T₀ space is a continuous poset equipped with the Scott topology in the specialization order iff its topology is completely distributive and coarser than or equal to the Scott topology;

(4)

A topological T₁ space is a discrete space iff its topology is completely distributive.

These results generalize the relevant results obtained by J.D. Lawson for dcpos.     

Adjunctions and Locally Transferable Factorization Systems

We present an approach to construct factorization systems in abstract categories. It gives new factorization systems from some given ones, when we have a relevant family of adjunctions between slice categories. The approach is based on the notion of a local factorization system, which is introduced in this paper. Relations between local factorization systems and full replete reflective subcategories of corresponding slice categories are investigated. Several applications of this approach are given.     

On fixpoint objects and gluing constructions

This article has two parts: in the first part, we present some general results about fixpoint objects. The minimal categorical structure required to model soundly the equational type theory which combines higher order recursion and computation types (introduced by Crole and Pitts (1992)) is shown to be precisely a let-category possessing a fixpoint object. Functional completeness for such categories is developed. We also prove that categories with fixpoint operators do not necessarily have a fixpoint object.In the second part, we extend Freyd's gluing construction for cartesian closed categories to cartesian closed let-categories, and observe that this extension does not obviously apply to categories possessing fixpoint objects. We solve this problem by giving a new gluing construction for a limited class of categories with fixpoint objects; this is the main result of the paper. We use this category-theoretic construction to prove a type-theoretic conservative extension result.     

连续偏序集及其Smyth幂的几个等权定理

推广连续D om a in的权的概念到连续偏序集上,探讨连续偏序集的权、相应内蕴拓扑的权、定向完备化的权以及Sm yth幂D om a in的权间的关系。得到了几个等权定理:(1)连续偏序集的权与其上Scott拓扑、L aw son拓扑的权相等;(2)连续偏序集的权与其定向完备化的权相等;(3)无穷连续D om a in的权与其Sm yth幂D om a in的权相等;(4)有限D om a in的权小于或等于它的Sm yth幂D om a in的权。     

B-posets, FS-posets and Relevant Categories

In this paper the new concept of B-posets is introduced. Some properties of B-posets and FS-posets are examined. Main results are: (1) Posets obtained from B-posets (FS-posets) by eliminating a proper upper subset, adding two or more finitely many incomparable maximal elements, taking vertical sums w.r.t. a maximal element are also B-posets (FS-posets); (2) A poset is a(n) B-domain (FS-domain) iff it is a Lawson compact B-poset (FS-poset); (3) The directed completions of B-posets (FS-posets) are B-domains (FS-domains); (4) The category B-POS (FS-POS) of B-posets (FS-posets) and Scott continuous maps is cartesian closed and has the category B-DOM (FS-DOM) of B-domains (FS-domains) and Scott continuous maps as a full reflective subcategory.     

The Category of S-Posets

In this paper, we consider some category-theoretic properties of the category Pos-S of all S-posets (posets equipped with a compatible right action of a pomonoid S), with monotone action-preserving maps between them. We first discuss some general category-theoretic ingredients of Pos-S; specifically, we characterize several kinds of epimorphisms and monomorphisms. Then, we present some adjoint relations of Pos-S with Pos, Set, and Act-S. In particular, we discuss free and cofree objects. We also examine other category-theoretic properties, such as cartesian closedness and monadicity. Finally, we consider projectivity in Pos-S with respect to regular epimorphisms and show that it is the same asprojectivity, although projectives are not generally retracts of free objects over posets.