English

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

Logic 2016-08-23 v3

Abstract

We present a self-contained account of Woodin's extender algebra and its use in proving absoluteness results, including a proof of the Σ12\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+\AD^+.

Keywords

Cite

@article{arxiv.1005.4193,
  title  = {The extender algebra and $\Sigma^2_1$-absoluteness},
  author = {Ilijas Farah},
  journal= {arXiv preprint arXiv:1005.4193},
  year   = {2016}
}

Comments

Minor upgrades and bug fixes

R2 v1 2026-06-21T15:26:40.533Z