English

Fine structure from normal iterability

Logic 2025-05-22 v5

Abstract

We show that (i) the standard fine structural properties for premice follow from normal iterability (whereas the classical proof relies on iterability for stacks of normal trees), and (ii) every mouse which is finitely generated above its projectum, is an iterate of its core. That is, let mm be an integer and let MM be an mm-sound, (m,ω1+1)(m,\omega_1+1)-iterable premouse. Then (i) MM is (m+1)(m+1)-solid and (m+1)(m+1)-universal, (m+1)(m+1) condensation holds for MM, and if m1m\geq 1 then MM is super-Dodd-sound, a slight strengthening of Dodd-soundness. And (ii) if there is xMx\in M such that MM is the rΣm+1\mathrm{r}\Sigma_{m+1}-hull of parameters in ρm+1M{x}\rho_{m+1}^M\cup\{x\}, then MM is a normal iterate of its (m+1)(m+1)-core C=Cm+1(M)C=\mathfrak{C}_{m+1}(M); in fact, there is an mm-maximal iteration tree T\mathcal{T} on CC, of finite length, such that M=MTM=M^{\mathcal{T}}_\infty, and i0Ti^{\mathcal{T}}_{0\infty} is just the core embedding. Applying fact (ii), we prove that if MZFCM\models\mathrm{ZFC} is a mouse and WMW\subseteq M is a ground of MM via a strategically σ\sigma-closed forcing PW\mathbb{P}\in W, and if M1MWM|\aleph_1^M\in W (that is, the initial segment of MM of height 1M\aleph_1^M is in WW), then the forcing is trivial; that is, MWM\subseteq W. And if there is a measurable cardinal, then there is a non-solid premouse. The results hold for premice with Mitchell-Steel indexing, allowing extenders of superstrong type to appear on the extender sequence.

Keywords

Cite

@article{arxiv.2011.10037,
  title  = {Fine structure from normal iterability},
  author = {Farmer Schlutzenberg},
  journal= {arXiv preprint arXiv:2011.10037},
  year   = {2025}
}

Comments

145 pages. Made minor corrections to proof of Theorem 11.3. (Especially Claim 2's proof; the earlier version appeared to be using stronger hypotheses than those available. Otherwise mostly corrected typos in the proof. Added footnote on page 92.)

R2 v1 2026-06-23T20:22:48.269Z