Paper detail

The consistency strength of long projective determinacy

We determine the consistency strength of determinacy for projective games of length $ω^2$. Our main theorem is that $\boldsymbolΠ^1_{n+1}$-determinacy for games of length $ω^2$ implies the existence of a model of set theory with $ω+ n$ Woodin cardinals. In a first step, we show that this hypothesis implies that there is a countable set of reals $A$ such that $M_n(A)$, the canonical inner model for $n$ Woodin cardinals constructed over $A$, satisfies $A = \mathbb{R}$ and the Axiom of Determinacy. Then we argue how to obtain a model with $ω+ n$ Woodin cardinal from this. We also show how the proof can be adapted to investigate the consistency strength of determinacy for games of length $ω^2$ with payoff in $\Game^\mathbb{R} \boldsymbolΠ^1_1$ or with $σ$-projective payoff.