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Intermediate behavior of forceably Σ_{n−1}-correct regular cardinals under Σ_n–CFA

Determine whether there exists a model of the Σ_n-correct forcing axiom Σ_n–CFA_{<κ}(Γ) (for n>2 and any n‑nice forcing class Γ) in which the class of regular cardinals that are forceably Σ_{n−1}-correct, i.e., ♦C^{(n−1)}∩Reg, is neither empty nor a proper class.

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Background

Section 3.3 studies whether increasing n in Σ_n-correct forcing axioms yields strictly stronger principles. The author introduces the class ♦C{(m)} of cardinals that become Σ_m-correct in some forcing extension.

Establishing a model where ♦C{(n−1)}∩Reg is neither empty nor a proper class would clarify whether the hierarchy can exhibit intermediate patterns at level n>2 and would inform strictness results between successive levels.

References

We are left with the following open questions, where a positive answer to the first would easily yield a positive answer to the second: Is it possible to produce a model of $\Sigma_n\mhyphen CFA_{<\kappa}(\Gamma)$ where $\diamondsuit C{(n-1)}\cap Reg$ is neither empty nor a proper class when $n>2$?

$Σ_n$-correct Forcing Axioms (2405.09674 - Goodman, 15 May 2024) in Section 3.3 (Do Σ_n-correct Forcing Axioms Form a Strict Hierarchy in n?)