Modal logics of almost sure validities in some classes of euclidean and transitive frames

Abstract

Given a class C of finite Kripke frames, we consider the uniform distribution on the frames from C with n states. A formula is almost surely valid in C if the probability that it is valid in a random C-frame with n states tends to 1 as n tends to infinity. The formulas that are almost surely valid in C form a normal modal logic. We find complete and sound axiomatizations for the logics of almost sure validities in the classes of finite frames defined by the logics K5, KD5, K45, KD45, K5B, S5, Grz.3, and GL.3.