csf可数空间的注记

讨论csf可数空间的性质,把csf可数空间刻画为度量空间的映像,同时探讨了伪紧的csf可数空间的第一可数性质,推广了Arhangel’skiˇ?关于度量空间伪开s映像的结果,证明了正则伪紧的仿拓扑群是可度量化的当且仅当它是csf可数的Fr′echet空间.     

正规可数仿紧空间的逆极限

得到了如下结果:设X是逆系统{Xα,παβ,Λ}的逆极限,|Λ|=λ,假设每个映射πα∶X→Xα是开的且到上的,X是λ-仿紧,每个Xα是正规可数仿紧的,则X是正规可数仿紧的.进一步得到了关于遗传正规且遗传可数仿紧空间的类似结果.     

仿紧空间和S-闭空间的共同推广

定义了仿S紧空间的概念,它是仿紧空间和S－闭空间的共同推广,文中讨论了仿S紧密空间的一些性质,推广了仿紧空间和S－闭空间的部分结果。     

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     

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.     

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".     

L-拓扑空间的层仿紧性

在L-拓扑空间中定义了一种新型的仿紧性,即层仿紧性,并研究其性质,讨论了这种仿紧性与已有的两种仿紧性之间的关系.     

遗传中紧空间与散射分解

本文证明了可数仿紧(中紧、亚紧)空间有类似Junnila的刻画，遗传中紧空间不具有类似Junnila的刻画，并给出了每个散射分解有紧有限的开膨胀的充要条件．     

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．     

L—fuzzy拓扑空间中的层仿紧集

首先，在Ｌ－ｆｕｚｚｙ拓扑空间中引入了强α－局部有限族，并以此定义了比Ⅱ型强仿紧性更为广泛的层仿紧性，且讨论了层仿紧集的基本性质。其次，针对Ｌ－ｆｕｚｚｙ子集引入了层Ｈａｕｓｄｏｒｆｆ分离性，研究了它的基本特征。最后，讨论了弱诱导包含式正则空间中层仿紧集的特征。     

Planar and affine spaces

In this note, we characterize finite three-dimensional affine spaces as the only linear spaces endowed with set Ω of proper subspaces having the properties (1) every line contains a constant number of points, say n, with n>2; (2) every triple of noncollinear points is contained in a unique member of Ω; (3) disjoint or coincide is an equivalence relation in Ω with the additional property that every equivalence class covers all points. We also take a look at the case n=2 (in which case we have a complete graph endowed with a set Ω of proper complete subgraphs) and classify these objects: besides the affine 3-space of order 2, two small additional examples turn up. Furthermore, we generalize our result in the case of dimension greater than three to obtain a characterization of all finite affine spaces of dimension at least 3 with lines of size at least 3.     

On the embedding of BV space into Besov-Orlicz space

We give a sufficient (and, in the case of a compact domain, a necessary) condition for the embedding of Sobolev space of functions with integrable gradient into Besov-Orlicz spaces to be bounded. The condition has a form of a simple integral inequality involving Young and weight functions. We provide an example with Matuszewska-Orlicz indices of involved Orlicz norm equal to one. The main tool is the molecular decomposition of functions from a BV space.     

Corrigendum to “Characterization of Sobolev and BV spaces” [J. Funct. Anal. 261 (10) (2011) 2926–2958]

We correct a mistake in [3].     

Countable compact Hausdorff spaces need not be metrizable in ZF

We show that the existence of a countable, first countable, zero-dimensional, compact Hausdorff space which is not second countable, hence not metrizable, is consistent with ZF.

     

The classical Banach spaces

In this paper we study some structural and geometric properties of the quotient Banach spaces , where is an arbitrary set, is an Orlicz function, is the corresponding Orlicz space on and , being the ideal of elements with finite support. The results we obtain here extend and complete the ones obtained by Leonard and Whitfield (Rocky Mountain J. Math. 13 (1983), 531-539). We show that is not a dual space, that , if for every , that has no smooth points, that it cannot be renormed equivalently with a strictly convex or smooth norm, that is a Grothendieck space, etc.

     

初始的L-外部空间

研究了初始的L-外部空间.构造了L-外部空间范畴的初始结构,并由此定义了L-外部空间的乘积结构和子空间结构,证明了L-外部空间范畴是L-预外部空间范畴的余反射子范畴.     

关于rectifiable空间中的局部(序列)连通性的几个注记

给出连通的rectifiable空间是局部序列连通(或局部连通)的刻画,推广了拓扑群中的相应结果;利用rectifiable空间G中e的局部邻域基给出G是局部连通(或局部序列连通)的刻画;证明了若A是rectifiable空间G中的序列开子集,那么H=A是G的序列开rectifiable子空间.     

Higher-order symmetrization inequalities and applications

We prove new extended forms of the Pólya-Szegö symmetrization principle. As a consequence new sharp embedding theorems for generalized Sobolev and Besov spaces are proved.     

Symmetrization inequalities in the fractional case and Besov embeddings

We prove new extended forms of the Pólya-Szegö symmetrization principle in the fractional case. As a consequence we determine new results for rearrangement invariant hulls of generalized Besov spaces.