کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4660609 1344376 2010 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
On metric spaces with the Haver property which are Menger spaces
موضوعات مرتبط
مهندسی و علوم پایه ریاضیات هندسه و توپولوژی
پیش نمایش صفحه اول مقاله
On metric spaces with the Haver property which are Menger spaces
چکیده انگلیسی

A metric space (X,d) has the Haver property if for each sequence ϵ1,ϵ2,… of positive numbers there exist disjoint open collections V1,V2,… of open subsets of X, with diameters of members of Vi less than ϵi and covering X, and the Menger property is a classical covering counterpart to σ-compactness. We show that, under Martin's Axiom MA, the metric square (X,d)×(X,d) of a separable metric space with the Haver property can fail this property, even if X2 is a Menger space, and that there is a separable normed linear Menger space M such that (M,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].

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Topology and its Applications - Volume 157, Issue 8, 1 June 2010, Pages 1495-1505