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.
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Natl Res Univ, Higher Sch Econ, Soyza Pechatnikov St 16, St Petersburg, RussiaCINVESTAV, Dept Matemat, Apartado Postal 14-740, Mexico City 07000, DF, Mexico