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Topic Archive: strongly unfoldable cardinal
Set theory seminarFriday, March 7, 201410:00 amGC6417
The consistency strength of PFA for posets preserving aleph_2 or aleph_3
The CUNY Graduate Center
While the consistency strength of PFA is quite high in the large cardinal hierarchy, it is reasonable to expect that tame fragments of PFA should require much weaker assumptions. I will present an argument of Hamkins and Johnstone (2008) which shows the consistency of PFA for posets preserving aleph_2 or aleph_3 from a strongly unfoldable cardinal, a much smaller large cardinal which is, roughly speaking, to strongness (or supercompactness) as weak compactness is to measurability.