#матлог #учёба #спецсеминар #не_мехмат #МИАН #ТД

Семинар отдела математической логики МИАН, Logic Online Seminar (www.mathnet.ru/rus/conf876), понедельник 16:00 MSK (UTC+3), Kontur Talk

25.05.2026 Simon Santschi (https://sisantschi.github.io/), Niels Vooijs (University of Bern, https://vooijs.pages.dev/academic/):

Interpolation above S4: completing Maksimova's classification (online talk)

A logic has Craig interpolation if for every valid implication "ϕ implies ψ", there exists an interpolant χ, using only variables that occur in both ϕ and ψ, such that "ϕ implies χ" and "χ implies ψ". Maksimova showed that at most 37 normal extensions of modal S4 have Craig interpolation. For the majority of these, Craig interpolation is known. However, for six cases this remained open. We complete Maksimova's classification by proving Craig Interpolation for these. The proof builds upon the standard Smoryński model construction, but employs a novel approach using Fine's frame formulas for splitting clusters.