Displaying similar documents to “Brauer-Kuroda relations for S-class numbers”

The spectrum of characters of ultrafilters on ω

Saharon Shelah (2008)

Colloquium Mathematicae

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We show the consistency of the statement: "the set of regular cardinals which are the characters of ultrafilters on ω is not convex". We also deal with the set of π-characters of ultrafilters on ω.