Duality and the PCF theory

by Shelah and Zapletal. [ShZa:791]
Math Research Letters, 2002
We consider natural cardinal invariants hm_n and prove several duality theorems, saying roughly: if I is a suitably definable ideal and provably cov (I) >= hm_n, then non (I) is provably small. The proofs integrate the determinacy theory, forcing and pcf theory.

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