PFA and the definability of the nonstationary ideal
Stefan HoffelnerPaul LarsonRalf SchindlerLiuzhen Wu
所有作者
Stefan HoffelnerPaul LarsonRalf SchindlerLiuzhen Wu
文献摘要
We produce, relative to a ZFC model with a supercompact cardinal, a ZFC model of the Proper Forcing Axiom in which the nonstationary ideal on ω1 is Π1-definable in a parameter from Hℵ2.