The spectrum of characters of ultrafilters on $\omega$
Tom 111 / 2008
Colloquium Mathematicum 111 (2008), 213-220
MSC: Primary 03E05, 03E17.
DOI: 10.4064/cm111-2-5
Streszczenie
We show the consistency of the statement: “the set of regular cardinals which are the characters of ultrafilters on $\omega $ is not convex”. We also deal with the set of $\pi $-characters of ultrafilters on $\omega $.
