On Loeb and sequential spaces in $\mathbf{ZF}$
Abstract
A topological space is called Loeb if the collection of all its non-empty closed sets has a choice function. In this article, in the absence of the axiom of choice, connections between Loeb and sequential spaces are investigated. Among other results, it is proved in that if is a Cantor completely metrizable second-countable space, then is Loeb. If a sequential, sequentially locally compact space has the property that every infinitely countable family of non-empty closed subsets of has a choice function, then the Cartesian product of with any sequential space is sequential. In consequence, it holds true in that the Cartesian product of a sequential locally countably compact space with any sequential space is sequential. If is sequential, then every second-countable compact Hausdorff space is sequential. It is also proved that, in some models of , a countable product of Cantor completely metrizable second-countable spaces can fail to be Loeb and it is independent of that every sequential subspace of is Loeb. Some other sentences are shown to be independent of . Several open problems are posed, among them, the following question: is sequential if is sequential?
Keywords
Cite
@article{arxiv.1904.06774,
title = {On Loeb and sequential spaces in $\mathbf{ZF}$},
author = {Kyriakos Keremedis and Eliza Wajch},
journal= {arXiv preprint arXiv:1904.06774},
year = {2019}
}