The inclusion of the second-order constructible universe in the first-order constructible universe

From papers

Let C(aa)C(\mathop{\text{aa}}) and C2(ω)C^2(\omega) denote the inner models defined in the paper, with C(aa)C(\mathop{\text{aa}}) the model generated using the relevant class of structures and C2(ω)C^2(\omega) the second-order constructible universe. Inclusion conjecture. Assuming appropriate large cardinals, we have

C(aa)C2(ω).C(\mathop{\text{aa}})\subset C^2(\omega).

This is a proposed relationship between the two inner models. The surrounding text gives related positive results under a proper class of Woodin cardinals and under MM++\text{MM}^{++} for reals and subsets of ω1\omega_1, but does not resolve the full inclusion.

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Sources & referencesView supporting material

Primary source

Menachem Magidor and Jouko Väänänen, “New inner models from second order logics”, arXiv:2508.17672 (2025).

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