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The necessity of κ-compactness for directedness of the Rudin–Keisler order
Conjecture on directedness. $ba$ -compactness, or large-cardinal principles of similar consistency strength, is necessary for the directedness of…
Conjectureopenlarge-cardinals rudin-keisler-order set-theoryarXiv posted 2 days ago
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Cardinality and Ramsey-ultrafilter conjecture for Rudin–Keisler intervals
Cardinality and Ramsey-ultrafilter conjecture. For every ultrafilter $\boldsymbol u$ ,
Problemopenrudin-keisler-order set-theoretic-topology ultrafiltersarXiv posted 2 days ago

The necessity of κ-compactness for directedness of the Rudin–Keisler order