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On \(T_3\)-topological space omitting many cardinals - MaRDI portal

On \(T_3\)-topological space omitting many cardinals (Q1964602)

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On \(T_3\)-topological space omitting many cardinals
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    On \(T_3\)-topological space omitting many cardinals (English)
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    21 February 2000
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    Following I. Juhász the set \(c\)-\(sp(X)=\{|A|\mid A\) is an infinite closed subspace of \(X\}\) is called the cardinality spectrum of the infinite topological space \(X\). For compact Hausdorff spaces its structure was studied by \textit{I. Juhász} [Isr. J. Math. 81, No. 3, 369-379 (1993; Zbl 0799.54002)] and by \textit{I. Juhász} and \textit{S. Shelah} [Fundam. Math. 155, No. 1, 91-94 (1998; Zbl 0896.54001)]. In this paper it is shown that for noncompact Hausdorff spaces the cardinality spectrum can have a large gap. More precisely, it is proved that for every infinite cardinal \(\kappa\) there exists a zero-dimensional Hausdorff space \(X\) with \(|X|=2^{2^{\kappa}}\) such that \(c\)-\(sp(X)\cap[\kappa,2^{2^{\kappa}})=\emptyset\).
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    zero-dimensional space
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    cardinality specrum
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