The notion of formal space was introduced by Fourman and Grayson [FG] only a few years ago, but it is only a recent though important step of a long story whose roots involve such names as Brouwer and… Expand

SummaryWithin the technical frame supplied by the algebraic variety of diagonalizable algebras, defined by R. Magari in [2], we prove the following:LetT be any first-order theory with a predicate Pr… Expand

On donne une demonstration simplifiee du theoreme de Sahlqvist sur la completude et la correspondance d'une large classe de formules modales, en se servant ici d'arguments topologiques.Expand

The duality between general frames and modal algebras allows to transfer a problem about the relational (Kripke) semantics into algebraic terms, and conversely we prove that the modal algebra A is subdirectly irreducible if and only if the dual frame A* is generated.Expand