On the Independent Axiomatizability of Modal and Intermediate Logics
Alexander Chagrov, Michael Zakharyaschev · Journal of Logic and Computation · 1995
This paper gives a solution to the old independent axiomatizability problem by presenting normal modal logics above K4 and Grz and an intermediate logic without independent axiomatizations. Incidentally Blok's problem is solved: the lattices of varieties of topological Boolean and pseudo-Boolean algebras are not strongly atomic. We also study the relationship between independent axiomatizability of intermediate logics and their modal companions above S4.