Cardinal inequalities for $S(n)$-spaces
General Topology
2018-11-01 v1
Abstract
Hajnal and Juh\'asz proved that if is a -space, then , and if is a Hausdorff space, then and . Schr\"oder sharpened the first two estimations by showing that if is a Hausdorff space, then , and if is a Urysohn space, then . In this paper, for any positive integer and some topological spaces , we define the cardinal functions , , , and , called respectively -character, -pseudocharacter, -spread, and -cellularity, and using these new cardinal functions we show that the above-mentioned inequalities could be extended to the class of -spaces. We recall that the -spaces are exactly the Hausdorff spaces and the -spaces are exactly the Urysohn spaces.
Cite
@article{arxiv.1810.12998,
title = {Cardinal inequalities for $S(n)$-spaces},
author = {Ivan S. Gotchev},
journal= {arXiv preprint arXiv:1810.12998},
year = {2018}
}
Comments
13 pages