The Chang-model cardinal-regularity conjecture

Let VV be a hod mouse and let λ\lambda be a Woodin limit of Woodin cardinals. Let gColl(ω,<λ)g\subseteq\operatorname{Coll}(\omega,<\lambda) be VV-generic, and let (j,M)(j,M) be as in the cited Chang-model theorem. Set ν=j(λ)\nu=j(\lambda) and N=j(Vλ)N=j(V_\lambda).

Cardinal-regularity conjecture. Then

Lν(Nω,Γg,Rg)ZF,L_\nu(N^\omega,\Gamma_g,\mathbb{R}_g)\vDash\mathsf{ZF},

and

Lν(Nω,Γg,Rg)“for every cardinal ηΘ,η+ is a regular cardinal”.L_\nu(N^\omega,\Gamma_g,\mathbb{R}_g)\vDash “\text{for every cardinal }\eta\geq\Theta,\\ \eta^+\text{ is a regular cardinal}”.

The conjecture concerns the structure above Θ\Theta in a determinacy model arising from a hod mouse. The paper presents this as an important question; its general validity remains open.

Sources & referencesView supporting material

Primary source

Douglas Blue, Paul B. Larson and Grigor Sargsyan, “Nairian Models”, arXiv:2501.18958 (2025).

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