The intermediate-model classification conjecture for Magidor–Radin forcing

Let GM[U]G\subseteq \mathbb{M}[\vec{U}] be a VV-generic filter, where

ακ  oU(α)α.\forall\alpha\leq\kappa\; o^{\vec{U}}(\alpha)\leq\alpha.

Let VMV[G]V\subseteq M\subseteq V[G] be a transitive ZFCZFC model. Intermediate-model classification conjecture. Either MM is a finite iteration of Magidor-like forcings as in the cited work, or there is a tree T[κ]<ωT\subseteq[\kappa]^{<\omega} in VV with ht(T)=ωht(T)=\omega such that, for every tTt\in T and every αSuccT(t)\alpha\in\operatorname{Succ}_T(t), there is a name M[U]tα\mathbb{M}[\vec{U}]^*_{t^{\smallfrown}\alpha} for a Magidor-like forcing. If HH is VV-generic for the forcing that adds a branch through TT together with the forcings M[U]tα\mathbb{M}[\vec{U}]^*_{t^{\smallfrown}\alpha} corresponding to that branch, then M=V[H]M=V[H]. The conjecture proposes a classification of all intermediate transitive ZFCZFC models between VV and the Magidor–Radin extension V[G]V[G], distinguishing finite iterations from models generated by a tree-indexed sequence of Magidor-like forcings.

Sources & referencesView supporting material

Primary source

Tom Benhamou and Moti Gitik, “Intermediate Models of Magidor-Radin Forcing- Part II”, arXiv:2105.11700 (2022).

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