Subspace of an ordinal;
countably compact space;
first countable space;
D-space Sokolov space;
function space;
Lindelof space;
iterated function space;
retraction;
D O I:
10.2989/16073606.2011.594237
中图分类号:
O1 [数学];
学科分类号:
0701 ;
070101 ;
摘要:
A space X is Sokolov if for any sequence {F(n) : n is an element of N} where F(n) is a closed subset of X(n) for every n is an element of N, there exists a continuous map f : X -> X such that nw (f(X)) <= omega and f(n) (F(n)) subset of F(n) for all n is an element of N. We prove that if X is a first countable countably compact subspace of an ordinal then X is a Sokolov space and Cp (X) is a D-space; this answers a question of Buzyakova. Thus, for any first countable countably compact subspace X of an ordinal, the iterated function space Cp; 2n + 1 (X) is Lindelof for any n is an element of omega. Another consequence of the above results is the existence of a fi rst countable Sokolov space of cardinality greater than c.
机构:
Louisiana State Univ, Dept Math, Baton Rouge, LA 70803 USALouisiana State Univ, Dept Math, Baton Rouge, LA 70803 USA
Lawson, Jimmie
Xu, Xiaoquan
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机构:
Minnan Normal Univ, Fujian Key Lab Granular Comp & Applicat, Zhangzhou 363000, Peoples R ChinaLouisiana State Univ, Dept Math, Baton Rouge, LA 70803 USA