title: On the Beth properties of some intuitionistic modal logics
abstract: Let L be one of the intuitionistic modal logics. As in the classical modal case, we define two different forms of the Beth property for L, which are denoted by B1 and B2; in this paper we study the relation among B1, B2 and the interpolation properties C1 and C2. It turns out that C1 implies B1, but contrary to the boolean case, is not equivalent to B1. It is shown that B2 and C2 are independent, and moreover it comes out that, in contrast to classical case, there exists an extension of the intuitionistic modal logic of S/sub 4/-type, that has not the property B2. Finally we give two algebraic properties, that characterize respectively B1 and B2
keyphrases: Beth properties intuitionistic modal logics interpolation properties