English

On resolvability of products

General Topology 2022-05-31 v1

Abstract

All spaces below are T0T_0 and crowded (i.e. have no isolated points). For nωn \le \omega let M(n)M(n) be the statement that there are nn measurable cardinals and Π(n)\Pi(n) (Π+(n)\Pi^+(n)) that there are n+1n+1 (0-dimensional T2T_2) spaces whose product is irresolvable. We prove that M(1),Π(1)M(1),\,\Pi(1) and Π+(1)\Pi^+(1) are equiconsistent. For 1<n<ω1 < n < \omega we show that CON(M(n))CON(M(n)) implies CON(Π+(n))CON(\Pi^+(n)). Finally, CON(M(ω))CON(M(\omega)) implies the consistency of having infinitely many crowded 0-dimensional T2T_2-spaces such that the product of any finitely many of them is irresolvable. These settle old problems of Malychin. Concerning an even older question of Ceder and Pearson, we show that the following are consistent modulo a measurable cardinal: (i) There is a 0-dimensional T2T_2 space XX with ω2Δ(X)2ω1\omega_2 \le \Delta(X) \le 2^{\omega_1} whose product with any countable space is not ω2\omega_2-resolvable, hence not maximally resolvable. (ii) There is a monotonically normal space XX with Δ(X)=ω\Delta(X) = \aleph_\omega whose product with any countable space is not ω1\omega_1-resolvable, hence not maximally resolvable. These significantly improve a result of Eckertson.

Keywords

Cite

@article{arxiv.2205.14896,
  title  = {On resolvability of products},
  author = {István Juhász and Lajos Soukup and Zoltán Szentmiklóssy},
  journal= {arXiv preprint arXiv:2205.14896},
  year   = {2022}
}

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17 pages