On extensions of intermediate logics by strong negation

In this paper we will study the properties of the least extension n(Λ) of a given intermediate logic Λ by a strong negation. It is shown that the mapping from Λ to n(Λ) is a homomorphism of complete lattices, preserving and reflecting finite model property, frame-completeness, interpolation and decidability. A general characterization of those constructive logics is given which are of the form n(A). This summarizes results that can be found already in [13, 14] and [4]. Furthermore, we determine the structure of the lattice of extensions of n(LC). © 1998 Kluwer Academic Publishers.