关于具有局部可数sn-网的空间

In this paper,spaces with a locally countable sn-network are discussed.It is shown that a space with a locally countable sn-network iff it is an snf-countable space with a locally countable k-network.As its application,almost-open and closed mappings(or finite-to-one and closed mapping) preserve locally countable sn-networks,and a perfect preimage theorem on spaces with a locally countable sn-network is established.     

星可数κ网与序列覆盖S映射

证明了在空间具有星可数κ网的条件下,度量空间的1(2)序列覆盖s映象是局部可分度量空间的1(2)序列覆盖、紧覆盖s映象.     

星可数k网与序列覆盖s映射

证明了在空间具有星可数ｋ网的条件下,度量空间的１（２）序列覆盖ｓ映象是局部可分度量空间的１（２）序列覆盖、紧覆盖ｓ映象。     

可数Sober空间的若干性质北大核心

可数sober空间是sober空间的一种推广.本文讨论了可数sober空间的一些性质,特别地证明了以可数sober空间为对象、以连续映射为态射的范畴CSOB为完备范畴以及从任意空间到可数sober空间的连续映射空间为可数sober空间.     

L-fuzzy拓扑空间中的几乎可数仿紧性

以可数仿紧性为背景,介绍几乎可数仿紧性的定义,并刻画其基本特征.深入研究L-fuzzy几乎可数仿紧性的性质,并证明几乎可敷仿紧性是"L-好的推广".     

拟第一可数空间和弱拟第一可数空间

讨论了拟第一可数空间和弱拟第一可数空间的遗传性和可积性,给出了一些反例来说明这两类空间在某些拓扑运算下的不封闭性,同时研究了它们具有遗传性和可积性的充要条件.     

局部可数集族、局部有限集族与Alexandroff问题

本文引进分层强ｓ－映射和分层强紧映射建立具有σ－局部可数网、具有σ－局部可数ｋ－网、具有σ－局部可数基的正则空间以及σ－空间、－空间、ｇ－可度量空间和确定的度量空间之间的联系．这些都是对Ａｌｅｘａｎｄｒｏｆｆ问题的回答．     

局部可数集族、局部有限集族与Alexandroff问题

本文引进分层强ｓ－映射和分层强紧映射建立具有σ－局部可数网、具有σ－局部可数ｋ－网、具有σ－局部可数基的正则空间以及σ－空间、－空间、ｇ－可度量空间和确定的度量空间之间的联系．这些都是对Ａｌｅｘａｎｄｒｏｆｆ问题的回答．     

Locally M-Pseudoconvex Topologies on Locally A-Pseudoconvex Algebras

Let (A, T) be a locally A-pseudoconvex algebra over or . We define a new topology m(T) on A which is the weakest among all m-pseudoconvex topologies on A stronger than T. We describe a family of non-homogeneous seminorms on A which defines the topology m(T).     

Concretely Locally Presentable and Locally Generated Categories

We give concrete versions of the characterizations of locally -presentable (resp. -generated) categories as categories of models of (resp. weakly) -ary limit-theories and of (resp. weakly) -ary essentially algebraic theories. By concrete we mean that starting with a category of -structures, the theories obtained are extensions of the original ones, and the equivalences of categories are concrete isomorphisms. -presentable and -generated objects are also investigated from this viewpoint.     

关于点可数序列邻域网

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Locally symmetric immersions

We use reflections with respect to submanifolds and related geometric results to develop, inspired by the work of Ferus and other authors, in a unified way a local theory of extrinsic symmetric immersions and submanifolds in a general analytic Riemannian manifold and in locally symmetric spaces. In particular we treat the case of real and complex space forms and study additional relations with holomorphic and symplectic reflections when the ambient space is almost Hermitian. The global case is also taken into consideration and several examples are given.     

局部可分度量空间的序列覆盖局部可数象

本文给出了局部可分度量空间的序列复盖局部可数象的刻画。     

Locally quasiconvex small-cancellation groups

In this article we prove several results about the local quasiconvexity behavior of small-cancellation groups. In addition to strengthening our previously obtained positive results, we also describe several families of negative examples. Also, as the strength of the assumed small-cancellation conditions increases, the gap between our positive results and our counterexamples narrows. Finally, as an additional application of these techniques, we include similar results and counterexamples for Coxeter groups.

     

Locally Factorisable Transformation Semigroups

A semigroup S is factorisable if S = GE = EG where G is a subgroup of S and E is the set of idempotents in S; and S is locally factorisable if eSe is factorisable for every e E. In this paper, we unify and extend results which characterise when certain transformation semigroups defined on a set are (locally) factorisable, and we consider the corresponding problem for the semigroup of linear transformations of a vector space.To Yupaporn Kemprasit, mentor of semigroup theorists in Thailand1991 Mathematics Subject Classification: 20M20The third section of this paper formed part of an MSc supervised by the first author. She greatly appreciates the help of her supervisor in this work; and the first two authors are grateful for the assistance of the third author in the preparation of this paper. The third author also acknowledges the generous support of Centro de Mathematica, Universidade do Minho, Portugal, during his visit in July–August 2000 when the paper was completed.     

局部有限超拓扑的局部紧性

本文讨论了赋予局部有限拓扑的非空闲子集超空间的局部紧性.主要结果是:X正则,则其闭子集超空间局部紧当且仅当X可表示成一个紧空间与一个离散空间的拓扑和.     

Continuous Selections and Locally Pseudocompact Groups

We characterize locally pseudocompact groups by means of the selection theory. Our result is the selection version of the well-known Comfort—Ross theorem on pseudocompactness which states that a topological group is pseudocompact if and only its Stone—Čech compactification is a topological group.