English

Supercompact minus compact is super

General Topology 2020-04-09 v1

Abstract

According to a folklore characterization of supercompact spaces, a compact Hausdorff space is supercompact if and only if it has a binary closed kk-network. This characterization suggests to call a topological space supersuper if it has a binary closed kk-network N\mathcal N. The binarity of N\mathcal N means that every linked subfamily of N\mathcal N is centered. Therefore, a Hausdorff space is supercompact if and only if it is super and compact. In this paper we prove that the class of super spaces contains all GO-spaces, all supercompact spaces, all metrizable spaces, and all collectionwise normal \aleph-spaces. Moreover, the class of super spaces is closed under taking Tychonoff products and discretely dense sets in Tychonoff products. The superness of metrizable spaces implies that each compact metrizable space is supercompact, which was first proved by Strok and Szyma\'nski (1975) and then reproved by Mills (1979), van Douwen (1981), and D{\c e}bski (1984).

Keywords

Cite

@article{arxiv.1906.03549,
  title  = {Supercompact minus compact is super},
  author = {Taras Banakh and Zdzisław Kosztołowicz and Sławomir Turek},
  journal= {arXiv preprint arXiv:1906.03549},
  year   = {2020}
}

Comments

17 pages

R2 v1 2026-06-23T09:47:56.707Z