The proper forcing axiom and stationary set reflection (Q1262859)

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scientific article; zbMATH DE number 4125398
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The proper forcing axiom and stationary set reflection
scientific article; zbMATH DE number 4125398

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    The proper forcing axiom and stationary set reflection (English)
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    1991
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    Our main result is that the proper forcing axiom (PFA) is equiconsistent with ``PFA \(+\) there is a nonreflecting stationary subset of \(\omega_ 2''\). More generally we show for any cardinals \(n<m\leq \aleph_ 2\) that if \(PFA^+(n)\) is consistent with ZFC then so is \(``PFA^+(n)\) \(+\) there are m mutually nonreflecting stationary subsets of \(\omega_ 2''\). As corollaries it follows that if \(n<m\leq \aleph_ 1\) then \(PFA^+(n)\) (if consistent) does not imply \(PFA^+(m)\), and that PFA (if consistent) does not imply Martin's maximum.
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    forcing axioms
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    stationary set reflection
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    proper forcing axiom
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    Martin's maximum
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