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arXiv · 1005.4193

The extender algebra and $\Sigma^2_1$-absoluteness

Ilijas Farah
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Abstract

We present a self-contained account of Woodin's extender algebra and its use in proving absoluteness results, including a proof of the $\Sigma^2_1$-absoluteness theorem. We also include a proof that the existence of an inner model with Woodin limit of Woodin cardinals implies the existence of divergent models of $\AD^+$.

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Ilijas Farah. 2010-05-23. The extender algebra and $\Sigma^2_1$-absoluteness. https://arxiv.org/abs/1005.4193

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