English

Second-countable compact Hausdorff spaces as remainders in $\mathbf{ZF}$ and two new notions of infiniteness

General Topology 2020-09-22 v1

Abstract

In the absence of the Axiom of Choice, necessary and sufficient conditions for a locally compact Hausdorff space to have all non-empty second-countable compact Hausdorff spaces as remainders are given in ZF\mathbf{ZF}. Among other independence results, the characterization of locally compact Hausdorff spaces having all non-empty metrizable compact spaces as remainders, obtained by Hatzenhuhler and Mattson in ZFC\mathbf{ZFC}, is proved to be independent of ZF\mathbf{ZF}. Urysohn's Metrization Theorem is generalized to the following theorem: every T3T_3-space which admits a base expressible as a countable union of finite sets is metrizable. Applications to solutions of problems concerning the existence of some special metrizable compactifications in ZF\mathbf{ZF} are shown. New concepts of a strongly filterbase infinite set and a dyadically filterbase infinite set are introduced, both stemming from the investigations on compactifications. Set-theoretic and topological definitions of the new concepts are given, and their relationship with certain known notions of infinite sets is investigated in ZF\mathbf{ZF}. A new permutation model is introduced in which there exists a strongly filterbase infinite set which is weakly Dedekind-finite. All ZFA\mathbf{ZFA}-independence results of this article are transferable to ZF\mathbf{ZF}.

Keywords

Cite

@article{arxiv.2009.09526,
  title  = {Second-countable compact Hausdorff spaces as remainders in $\mathbf{ZF}$ and two new notions of infiniteness},
  author = {Kyriakos Keremedis and Eleftherios Tachtsis and Eliza Wajch},
  journal= {arXiv preprint arXiv:2009.09526},
  year   = {2020}
}