$P$-spaces in the absence of the Axiom of Choice

Abstract

A $P$-space is a topological space whose every $G_{\delta }$-set is open. In this article, basic properties of $P$-spaces are investigated in the absence of the Axiom of Choice. New weaker forms of the Axiom of Choice, all relevant to $P$-spaces or to countable intersections of $G_{\delta }$-sets, are introduced. Several independence results are obtained and open problems are posed. It is shown that a zero-dimensional subspace of the real line may fail to be strongly zero-dimensional in $\mathbf{ZF}$. Among the open problems there is the question whether it is provable in $\mathbf{ZF}$ that every finite product of $P$-spaces is a $P$-space. A partial answer to this question is given.

References in corpus (1)

• On densely complete metric spaces and extensions of uniformly continuous functions in $\mathbf{ZF}$