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For each n, let n mean "the sentence is true in all ₍+₁-correct transitive sets. " Assuming G\"odel's axiom V = L, we prove the following graded variant of Solovay's completeness theorem: the set of formulas valid under this interpretation is precisely the set of theorems of the linear provability logic GLP. 3. We also show that this result is not provable in ZFC, so the hypothesis V = L cannot be removed. As part of the proof, we derive (in ZFC) the following purely modal-logical results which are of independent interest: the logic GLP. 3 coincides with the logic of closed substitutions of GLP, and is the maximal non-degenerate, normal extension of GLP.
Aguilera et al. (Fri,) studied this question.