English

The class $C({\omega}_1)$ and countable net weight

General Topology 2024-02-27 v2

Abstract

Hart and Kunen, and independently in the recent preprint arXiv:2304.13113, R\'ios-Herrej\'on defined and studied the class C(ω1)C({\omega}_1) of topological spaces XX having the property that for every neighborhood assignment {U(y):yY}\{U(y) : y \in Y\} with Y[X]ω1Y \in [X]^{\omega_1} there is Z[Y]ω1Z \in [Y]^{\omega_1} such that Z{U(z):zZ}.Z \subset \bigcap \{U(z) : z \in Z\}. It is obvious that spaces of countable net weight, i.e. having a countable network, belong to this class. In this paper we present several independence results concerning the relationships of these and several other classes that are sandwiched between them. These clarify some of the main problems that were raised in the above preprint. In particular, we prove that the continuum hypothesis, in fact a weaker combinatorial principle called super stick, implies that every regular space in C(ω1)C(\omega_1) has countable net weight, answering a question that was raised by Hart and Kunen.

Keywords

Cite

@article{arxiv.2307.11014,
  title  = {The class $C({\omega}_1)$ and countable net weight},
  author = {István Juhász and Lajos Soukup and Zoltán Szentmiklóssy},
  journal= {arXiv preprint arXiv:2307.11014},
  year   = {2024}
}

Comments

14 pages, extended and revised version

R2 v1 2026-06-28T11:36:08.485Z