The character spectrum of beta(N)
General Topology
2011-07-26 v3 Logic
Abstract
We show the consistency of: the set of regular cardinals which are the character of some ultrafilter on omega can be quite chaotic, in particular not only can be not convex but can have many gaps. We also deal with the set of pi-characters of ultrafilters on omega.
Cite
@article{arxiv.1004.2083,
title = {The character spectrum of beta(N)},
author = {Saharon Shelah},
journal= {arXiv preprint arXiv:1004.2083},
year = {2011}
}