English

Tameness for set theory $II$

Logic 2020-03-17 v1

Abstract

The paper is the second of two and shows that (assuming large cardinals) set theory is a tractable (and we dare to say tame) first order theory when formalized in a first order signature with natural predicate symbols for the basic definable concepts of second and third order arithmetic, and appealing to the model-theoretic notions of model completeness and model companionship. Specifically we use the general framework linking generic absoluteness results to model companionship introduced in the first paper to show that strong forms of Woodin's axiom ()(*) entail that any theory TT extending ZFC\mathsf{ZFC} by suitable large cardinal axioms has a model companion TT^* with respect to certain signatures τ\tau containing symbols for Δ0\Delta_0-relations and functions, constant symbols for ω\omega and ω1\omega_1, a predicate symbol for the nonstationary ideal on ω1\omega_1, symbols for certain lightface definable universally Baire sets. Moreover TT^* is axiomatized by the Π2\Pi_2-sentences ψ\psi for τ\tau such that TT proves that L(\mathsf{UB})\models(\mathbb{P}_\max\Vdash\psi^{H_{\omega_2}}), where L(UB)L(\mathsf{UB}) denotes the smallest transitive model containing the universally Baire sets. Key to our results is the recent breakthrough of Asper\`o and Schindler establishing that a strong form of Woodin's axiom ()(*) follows from MM++\mathsf{MM}^{++}.

Keywords

Cite

@article{arxiv.2003.07120,
  title  = {Tameness for set theory $II$},
  author = {Matteo Viale},
  journal= {arXiv preprint arXiv:2003.07120},
  year   = {2020}
}
R2 v1 2026-06-23T14:15:57.424Z