Equiconsistencies at subcompact cardinals

We present equiconsistency results at the level of subcompact cardinals. Assuming SBHδ, a special case of the Strategic Branches Hypothesis, we prove that if δ is a Woodin cardinal and both 2(δ) and 2δ fail, then δ is subcompact in a class inner model. If in addition 2(δ+ ) fails, we prove that δ is Π2 1 subcompact in a class inner model. These results are optimal, and lead to equiconsistencies. As a corollary we also see that assuming the existence of a Woodin cardinal δ so that SBHδ holds, the Proper Forcing Axiom implies the existence of a class inner model with a Π2 1 subcompact cardinal. Our methods generalize to higher levels of the large cardinal hierarchy, that involve long extenders, and large cardinal axioms up to δ is δ+(n) supercompact for all n < ω. We state some results at this level, and indicate how they are proved. MSC 2010: 03E45, 03E55.

• Type: Journal
• Year: 2016
• Where: AML
• Authors: Itay Neeman, John R. Steel
• Keywords: Algorithms, AML 2016