Geometry of Robinson consistency in Łukasiewicz logic

Abstract

We establish the Robinson joint consistency theorem for the infinite-valued propositional logic of Łukasiewicz. As a corollary we easily obtain the amalgamation property for MV-algebras-the algebras of Łukasiewicz logic: all pre-existing proofs of this latter result make essential use of the Pierce amalgamation theorem for abelian lattice-ordered groups (with strong unit) together with the categorical equivalence Γ between these groups and MV-algebras. Our main tools are elementary and geometric.