Nagata's conjecture and countably compact hulls in generic extensions

被引:4
|
作者
Soukup, Lajos [1 ]
机构
[1] Hungarian Acad Sci, Alfred Renyi Inst Math, Budapest, Hungary
基金
匈牙利科学研究基金会;
关键词
countably compact; compactification; countably-compactification; countably compact hull; countably compactifiable; first countable; maximal first countable extension; M-space; forcing; Martin's Axiom; Nagata's conjecture;
D O I
10.1016/j.topol.2007.04.012
中图分类号
O29 [应用数学];
学科分类号
070104 ;
摘要
Nagata conjectured that every M-space is homeomorphic to a closed subspace of the product of a countably compact space and a metric space. Although this conjecture was refuted by Burke and van Douwen, and A. Kato, independently, but we can show that there is a c.c.c. poset P of size 2(omega) such that in V-P Nagata's conjecture holds for each first countable regular space from the ground model (i.e. if a first countable regular space X epsilon V is an M-space in V-P then it is homeomorphic to a closed subspace of the product of a countably compact space and a metric space in V-P). By a result of Morita, it is enough to show that every first countable regular space from the ground model has a first countable countably compact extension in V-P. As a corollary, we also obtain that every first countable regular space from the ground model has a maximal first countable extension in model V-P. (c) 2007 Elsevier B.V. All rights reserved.
引用
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页码:347 / 353
页数:7
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