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Paracompact subspaces in the box product topology

Authors: Peter Nyikos and Leszek Piatkiewicz
Journal: Proc. Amer. Math. Soc. 124 (1996), 303-314
MSC (1991): Primary 54D18; Secondary 54B10
MathSciNet review: 1327033
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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.

References [Enhancements On Off] (What's this?)

  • vD E. K. van Douwen, The box product of countably many metrizable spaces need not be normal, Fund. Math. 88 (1975), 127--132, MR 52:6640.
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Additional Information

Peter Nyikos

Leszek Piatkiewicz

Keywords: Paracompact space, box product
Received by editor(s): June 9, 1993
Additional Notes: The first author’s research was supported in part by NSF Grant DMS-8901931.
Communicated by: Franklin D. Tall
Article copyright: © Copyright 1996 American Mathematical Society

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