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Paracompact subspaces in the box product topology
Authors:Peter Nyikos   Leszek Piatkiewicz
Affiliation:Department of Mathematics, University of South Carolina, Columbia, South Carolina 29208 ; Department of Mathematics and Computer Science, Pembroke State University, Pembroke, North Carolina 28372
Abstract:In 1975 E. K. van Douwen showed that if $( X_n )_{ n in omega }$ is a family of Hausdorff spaces such that all finite subproducts $prod _{ n < m } X_n$ are paracompact, then for each element $x$ of the box product $square _{n in omega } X_n$ the $sigma $-product $sigma ( x ) = { y in square _{n in omega } X_n : { n in omega : x (n) neq y (n) } text{ is finite} }$ is paracompact. He asked whether this result remains true if one considers uncountable families of spaces. In this paper we prove in particular the following result: Theorem. Let $kappa $ be an infinite cardinal number, and let $( X_{alpha } )_{alpha in kappa }$ be a family of compact Hausdorff spaces. Let $x in square = square _{alpha in kappa } X_alpha $ be a fixed point. Given a family $mathcal{R}$ of open subsets of $square $ which covers $sigma ( x )$, there exists an open locally finite in $square $ refinement $mathcal{S}$ of $mathcal{R} $ which covers $sigma ( x )$.

We also prove a slightly weaker version of this theorem for Hausdorff spaces with ``all finite subproducts are paracompact" property. As a corollary we get an affirmative answer to van Douwen's question.

Keywords:Paracompact space   box product
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