A splitting logic in NExt(KTB)
The author initially relates subdirectly irreducible modal algebras (s.i. algebras) with general frames for modal logics. The author shows that every descriptive KTB frame which is connected corresponds to an s.i. KTB algebra. Thus, connected KTB frames can be regarded as building blocks of KTB logics. Next, the author shows that the normal modal logic of a Kripke frame of two reflexive points joint with a symmetric relation splits the lattice of all normal extensions of the logic KTB and, with this, that there exists a unique largest logic in the class of all normal extensions of KTB.
scientific article; zbMATH DE number 5189071
scientific article