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Fundamenta Mathematicae

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On resolvability of products

Volume 260 / 2023

Fundamenta Mathematicae 260 (2023), 281-295 MSC: Primary 54A25; Secondary 54A35, 03E35, 03E55. DOI: 10.4064/fm244-10-2022 Published online: 5 December 2022

Abstract

All spaces below are $T_0$ and crowded (i.e. have no isolated points).

For $n \le \omega$ let $M(n)$ be the statement that there are $n$ measurable cardinals, and $\Pi (n)$ ($\Pi ^+(n)$) that there are $n+1$ (0-dimensional $T_2$) spaces whose product is irresolvable. We prove that $M(1)$, $\Pi (1)$ and $\Pi ^+(1)$ are equiconsistent. For $1 \lt n \lt \omega$ we show that ${\rm CON}(M(n))$ implies ${\rm CON}(\Pi ^+(n))$. Finally, ${\rm CON}(M(\omega ))$ implies the consistency of having infinitely many crowded 0-dimensional $T_2$ spaces such that the product of any finitely many of them is irresolvable. These settle old problems of Malykhin (1973).

Concerning an even older question of Ceder and Pearson (1967), we show that the following are consistent modulo a measurable cardinal:

(i) There is a 0-dimensional $T_2$ space $X$ with $\omega _2 \le \Delta (X) \le 2^{\omega _1}$ whose product with any countable space is not $\omega _2$-resolvable, hence not maximally resolvable.

(ii) There is a monotonically normal space $X$ with $\Delta (X) = \aleph _\omega$ whose product with any countable space is not $\omega _1$-resolvable, hence not maximally resolvable.

These significantly improve a result of Eckertson (1997).

Authors

• István JuhászAlfréd Rényi Institute of Mathematics
Eötvös Loránd Research Network
H-1053, Budapest, Hungary
e-mail
• Lajos SoukupAlfréd Rényi Institute of Mathematics
Eötvös Loránd Research Network
H-1053, Budapest, Hungary
e-mail
• Zoltán SzentmiklóssyEötvös University of Budapest
H-1117, Budapest, Hungary
e-mail

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