Undecidability and non-axiomatizability of modal many-valued logics [article]

Amanda Vidal
2022 arXiv   pre-print
In this work we study the decidability of a class of global modal logics arising from Kripke frames evaluated over certain residuated lattices, known in the literature as modal many-valued logics. We exhibit a large family of these modal logics which are undecidable, in contrast with classical modal logic and propositional logics defined over the same classes of algebras. This family includes the global modal logics arising from Kripke frames evaluated over the standard Lukasiewicz and Product
more » ... lgebras. We later refine the previous result, and prove that global modal Lukasiewicz and Product logics are not even recursively axiomatizable. We conclude by solving negatively the open question of whether each global modal logic coincides with its local modal logic closed under the unrestricted necessitation rule.
arXiv:2101.08767v2 fatcat:effdf4mpqfehlmrqcctjbutv2q