Compact covering and game determinacy

被引:17
|
作者
Debs, G [1 ]
Raymond, JS [1 ]
机构
[1] UNIV PARIS 06,EQUIPE ANAL,F-75252 PARIS 05,FRANCE
关键词
compact covering; inductively perfect; determinacy;
D O I
10.1016/0166-8641(95)00058-5
中图分类号
O29 [应用数学];
学科分类号
070104 ;
摘要
All spaces are separable and metrizable. Suppose that the continuous and onto mapping f:X --> Y is compact covering. Under the axiom of Sigma(1)(1)-determinacy, we prove that f is inductively perfect whenever X is Borel, and it follows then that Y is also Borel. Under the axiom N-1(L) = N-i We construct examples showing that the conclusion might fail if ''X is Borel'' is replaced by ''X is coanalytic''. If we suppose that both X and Y are Borel,then we prove (in ZFC) the weaker conclusion that f has a Borel (in fact a Baire-1) section g:Y --> X. We also prove (in ZFC) that if we suppose only X to be Borel but of some ''low'' class, then Y is also Borel of the same class, Other related problems are discussed.
引用
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页码:153 / 185
页数:33
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