Every crowded pseudocompact ccc space is resolvable (Q330054)

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scientific article; zbMATH DE number 6642739
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Every crowded pseudocompact ccc space is resolvable
scientific article; zbMATH DE number 6642739

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    Every crowded pseudocompact ccc space is resolvable (English)
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    24 October 2016
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    \textit{E. Hewitt} [Duke Math. J. 10, 309--333 (1943; Zbl 0060.39407)] posed a set-theoretic topology problem: under which conditions can a topological space be resolved into two complementary sets each of which is dense in the given space. A Tychonoff space \(X\) is \(\mathfrak{\kappa}\)-resolvable (cardinal \(\mathfrak{\kappa}\geq 2\)) if \(X\) has a family of \(\mathfrak{\kappa}\)-many pairwise disjoint dense subsets of \(X\), and \(resolvable\) if \(\mathfrak{\kappa}=2\). \textit{W. W. Comfort} and \textit{S. García-Ferreira} [Topology Appl. 74, No. 1--3, 149--167 (1996; Zbl 0866.54004)] showed that every countably completely regular Hausdorff space with no isolated points (i.e., crowded) is \(\mathfrak{\omega}\)-resolvable, and asked whether every Tychonoff pseudocompact crowded space is resolvable. \textit{E. G. Pytkeev} [in: Algebra, topology, mathematical analysis. Transl. from the Russian. Moscow: Maik Nauka/Interperiodica. S152-S154 (2002; Zbl 1120.54304)] improved their result to: every countably compact crowded space is \(\mathfrak{\omega}_1\)-resolvable. \textit{I. Juhász} et al. left open the question [Topology Appl. 154, No. 1, 144--154 (2007; Zbl 1109.54004)] whether \(\mathfrak{\omega}_1\) can be improved to \(\mathfrak{c}\). This paper proves that if \(X\) is pseudocompact, crowded, and satisfies the countable chain condition (abbreviated as ccc, i.e., any family consisting of pairwise disjoint non-empty open sets is countable), then \(X\) is \(\mathfrak{c}\)-resolvable, thus partially answering the above questions, two decades after the author's conversations with Comfort and García-Ferreira. Very roughly, the paper uses the fact that a pseudocompact space \(X\) is \(G_\delta\)-dense in its Stone-Čech compactification \(\beta X\), and constructs a tree of non-empty sets in \(\beta X\), splitting \(X\) into \(\mathfrak{c}\)-many pairwise disjoint dense subsets. Souslin's Theorem [\textit{K. Kunen} et al., Pr. Nauk. Uniw. Śląsk. Katowicach 752, Ann. Math. Silesianae 2(14), 98--107 (1986; Zbl 0613.54018)] guarantees a Cantor set in \(X\).
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    resolvable
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    irresolvable
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    pseudocompact
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    countably compact
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    inverse system
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    zero-set
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