On metric spaces with the Haver property which are Menger spaces

被引:2
|
作者
Pol, Elzbieta [1 ]
Pol, Roman [1 ]
机构
[1] Univ Warsaw, Inst Matemat, PL-02097 Warsaw, Poland
关键词
Haver property; Property C; Menger property; Product spaces; Martin's Axiom; SELECTIVE SCREENABILITY; DIMENSIONAL SPACES; CARTESIAN PRODUCTS; SQUARE;
D O I
10.1016/j.topol.2009.03.054
中图分类号
O29 [应用数学];
学科分类号
070104 ;
摘要
A metric space (X, d) has the Haver property if for each sequence epsilon(1), epsilon(2), of positive numbers there exist disjoint open collections V-1, V-2. of open subsets of X, with diameters of members of V-1 less than epsilon(1) and boolean OR(infinity)(i=1) V-1 covering X. and the Meager property is a classical covering counterpart to sigma-compactness We show that. under Maitm's Axiom MA. the metric square (X, d) x (X, d) of a separable metric space with the Haver property can fail this property, even if X-2 is a Meager space. and that there is a separable normed linear Meager space M such that (A4 d) has the Haver property for every translation invariant metric d generating the topology of M, but not for every metric generating the topology These results answer some questions by L Babinkostova [L. Babinkostova. When does the Haver property imply selective screenability? Topology Appl 154 (2007) 1971-1979. L Babinkostova. Selective screenability in topological groups, Topology Appl 156 (1) (2008) 2-9] (C) 2009 Elsevier B V All rights reserved
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页码:1495 / 1505
页数:11
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