$G_\delta$-topology and compact cardinals
Abstract
For a topological space , let be the space with -topology of . For an uncountable cardinal , we prove that the following are equivalent: (1) is -strongly compact. (2) For every compact Hausdorff space , the Lindel\"of degree of is . (3) For every compact Hausdorff space , the weak Lindel\"of degree of is . This shows that the least -strongly compact cardinal is the supremum of the Lindel\"of and the weak Lindel\"of degrees of compact Hausdorff spaces with -topology. We also prove the least measurable cardinal is the supremum of the extents of compact Hausdorff spaces with -topology. For the square of a Lindel\"of space, using weak -topology, we prove that the following are consistent: (1) the least -strongly compact cardinal is the supremum of the (weak) Lindel\"of degrees of the squares of regular Lindel\"of spaces. (2) The least measurable cardinal is the supremum of the extents of the squares of regular Lindel\"of spaces.
Keywords
Cite
@article{arxiv.1709.07991,
title = {$G_\delta$-topology and compact cardinals},
author = {Toshimichi Usuba},
journal= {arXiv preprint arXiv:1709.07991},
year = {2018}
}