Free algebras, amalgamation, and a theorem of Vaught for many valued logics

Abstract

We investigate atomicity of free algebras and various forms of amalgamation for BL and MV algebras, and also Heyting algebras, though the latter algebras may not be linearly ordered, so strictly speaking their corresponding intuitionistic logic does not belong to many valued logic. Generalizing results of Comer proved in the classical first order case; working out a sheaf duality on the Zarski topology defined on the prime spectrum of such algebras, we infer several definability theorems, and obtain a representation theorem for theories as continuous sections of Sheaves. We also prove an omitting types theorem for fuzzy logic, and formulate and prove several of its consequences (in classical model theory) adapted to our case; that has to do with existence and uniqueness of prime and atomic models.