正规强可遮空间的逆极限性质

证明了如下结果:设X=lim/←{Xσ,πσρ,Λ),|A|=λ,并且每个投射πσ∶X→Xσ是开满的,(A)若X是λ-仿紧的并且每个Xσ是正规强可遮空间,则X是正规强可遮空间;(B)若X是遗传λ-仿紧的并且每个Xσ是遗传正规且遗传强可遮空间,则X是遗传正规强可遮空间.     

几乎仿紧空间

主要证明了如下结果 :( 1 )如果 X =∏α∈ΛXα是 |Λ | -仿紧空间 ,则 X是几乎仿紧 (仿 - L indelof)空间当且仅当 F∈ [Λ ]<ω,∏α∈ FXα是几乎仿紧 (仿 - L indelof)空间 .( 2 )如果 X =∏i∈ωXi 是可数仿紧的 ,则下列三条等价 :X是几乎仿紧 (仿 - L indelof)的 : F∈ [ω]<ω,∏i∈ FXi是几乎仿紧 (仿 - L indelof)的 : n∈ω,∏i≤ nXi是几乎仿紧 (仿- Lindelof)的 .最后还给出了几乎仿紧 (仿 - L indelof)空间的一个刻划     

正规狭义拟仿紧的乘积性质

本文主要证明了如下一些结果：（１）设Ｘ＝Ｌｉｍ并且每个投射πσ是开满映射，如果Ｘ是－仿紧的且每个 Ｘσ是正规狭义拟仿紧的，则 Ｘ是正规狭义拟仿紧的；如果 Ｘ是遗传－仿紧的且每个 Ｘσ是遗传正规狭义拟仿紧的．则 Ｘ是遗传正规狭义拟仿紧的． （２）如果 Ｘ＝是 －仿紧空间，则Ｘ是正规狭义拟仿紧的当且仅当 是正规狭义拟仿紧的．最后，还给出了诸多覆盖性质的可数乘积的一个等价性命题．     

再论集体次正规空间的逆极限

首先给出集体次正规空间的一组等价刻画.利用该组刻画证明:设X=lim{Xσ,πρσ,∑}并且每个投影映射πσ:X→Xσ是开满映射, (1)如果X是|∑|-仿紧的且每个Xσ是集体次正规空间,则X是正规集体次正规空间; (2)如果X是遗传|∑|-仿紧的且每个Xσ是遗传集体次正规空间,则X是遗传集体次正规空间.然后,在X=Ⅱα∈AXα是|A|-仿紧的条件下得到结果:X是集体次正规的当且仅当(?)F∈[A]<ω,Ⅱσ∈FXσ是集体次正规的,并且遗传集体次正规也有类似性质.     

p-仿紧空间

本文研究了p-仿紧空间和p-可数仿紧空间的相关问题.利用预开集和覆盖性质理论,得到了p-仿紧空间和p-可数仿紧空间的定义、等价刻画及αp-仿紧子集的性质,推广了一般拓扑学中仿紧空间的部分结果.     

关于遗传可遮和遗传σ-亚紧可数乘积的注记

证明了在逆序列的情形下,可遮空间、强可遮空间在假设X是可数仿紧空间的条件下可被其极限空间保持,进一步证明了遗传可遮,遗传强可遮及遗传σ-亚紧性在无需对投射及极限空间X做任何假设的情况下即可被其逆极限空间保持.作为上述两个结果的应用,分别给出了两个相关的可数Tychonoff乘积定理.     

正规可遮空间的逆极限

本文得到如下结果：设Ｘ是逆系统｛Ｘα，π＾αβ，Ａ｝的极限，│Λ│＝λ，假设每个投射πα：Ｘ→Ｘα是开且到上的，Ｘ是λ－仿紧的，如果每个Ｘα是正规可遮的，则Ｘ是仿紧的。进一步得到了关于遗传正规且遗传可遮的类似结果。     

关于紧序数空间可数次箱积的仿紧性

本文证明了如果对每个可数序数α,紧序数α+1的可数次箱积的商空间▽~ω(α+1)是特殊仿紧的,则对任意一个序数λ,▽~ω(λ+1)也是特殊仿紧的.     

正规弱δθ-可加空间的逆极限

本文证明了如下结果：设X＝lin←{Xσ，πρ^σ∧},|∧|＝λ，并且每个投身πσ：X→Xσ是开满射，（a)．若X是λ－仿紧的并且每个Xσ是正规弱δθ-可加空间，则X是正规弱δθ-可加空间；（b)．若X是λ－仿紧的并且每个Xσ是遗传正规的遗传弱δθ-可加，则X是遗传正规的遗传弱δθ-可加空间。     

σ-ortho紧的逆极限性质

主要证明了如下结果：设X=lim{Xσ，πρ^σ，∧}|∧||=λ，并且每个投射πσ：X→Xσ是开满映,若X是λ-仿紧的，并且每个Xσ是σ-ortho紧空间，则X是σ-ortho紧空间。进一步还可得到遗传σ-ortho紧性质的类似结果。     

A topological space is strongly paracompact if and only if for any monotone increasing open cover of it there exists a star-finite open refinement

We get the following result. A topological space is strongly paracompact if and only if for any monotone increasing open cover of it there exists a star-finite open refinement. We positively answer a question of the strongly paracompact property.     

Strong paracompactness and w- -refinability of inverse limits

In this paper we construct inverse systems of which each space is strongly paracompact and each bonding map and each projection are open and onto maps, and the limit space is paracompact and not strongly paracompact and we investigate -refinability-like properties of limit spaces of inverse systems.

     

实值函数与某些覆盖性质

In the paper [properties defined with semi-continuous functions and some related spaces',Houston J.Math.,2015,41(3):1097–1106] properties(U L)~(wl)_m,(U L)~K_m and(U L)_m were defined and it was shown that spaces having these properties coincide with countably paracompact spaces,countably mesocompact spaces and countably metacompact spaces,respectively.In this paper,we continue with the study on the relationship between properties defined with real-valued functions and some covering properties.Some characterizations of countably compact spaces and pseudo-compact spaces in terms of real-valued functions are obtained.     

关于纤维一般拓扑的一点注记(英文)

Some characterizations of paracompact maps are given in this note, and some equivalent statements of collectionwise normal maps are discussed. And also we show that if f ： X→Y is a closed collectionwise normal map, and f^-1（y） is a semistratifiable subspace of X for any y ∈ Y, then f is a paracompact map.     

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".     

Densely Continuous Forms in Vietoris Hyperspaces

For countably paracompact normal spaces X and locally compact separable metric spaces Y, a characterization is given for the closure of the set of densely continuous forms from X to Y in the hyperspace of nonempty closed subsets of X × Y under the Vietoris topology. This shows that for such X having no isolated points, every closed subset of X × R that is dense over X can be Vietoris approximated by a semicontinuous function on X.     

Monotonically countably paracompact, collectionwise Hausdorff spaces and measurable cardinals

We show that, if an MCP (monotonically countably paracompact) space fails to be collectionwise Hausdorff, then there is a measurable cardinal and that, if there are two measurable cardinals, then there is an MCP space that fails to be collectionwise Hausdorff.

     

On Countably Generated Dimension

In this article,we introduce and study the concept of countably generated dimension,which is a Krull-like dimension extension of the concept of DCC on countably generated submodules.We show that some of the basic results of Krull dimension are true for countably generated dimension.It is shown that an R-module M has Krull dimension if and only if it has countably generated dimension,and its Krull dimension and countably generated dimension coincide.     

A note on monotonically metacompact spaces

We show that any metacompact Moore space is monotonically metacompact and use that result to characterize monotone metacompactness in certain generalized ordered (GO) spaces. We show, for example, that a generalized ordered space with a σ-closed-discrete dense subset is metrizable if and only if it is monotonically (countably) metacompact, that a monotonically (countably) metacompact GO-space is hereditarily paracompact, and that a locally countably compact GO-space is metrizable if and only if it is monotonically (countably) metacompact. We give an example of a non-metrizable LOTS that is monotonically metacompact, thereby answering a question posed by S.G. Popvassilev. We also give consistent examples showing that if there is a Souslin line, then there is one Souslin line that is monotonically countable metacompact, and another Souslin line that is not monotonically countably metacompact.     

S-paracompact spaces

Summary We introduce the class of S-paracompact spaces as a generalization of paracompact spaces. A space (X,T) is S-paracompact if every open cover of X has a locally finite semi-open refinement. We characterize S-paracompact spaces and study their basic properties. The relationships between S-paracompact spaces and other well-known spaces are investigated.