Sahlqvist preservation for topological fixed-point logic
Nick Bezhanishvili, Sumit Sourabh · Journal of Logic and Computation · 2015
We introduce a new order-topological semantics for the positive modal mu-calculus over modal compact Hausdorff spaces, which are generalizations of descriptive frames. We define Sahlqvist sequents in this language, prove Esakia's lemma and Sahlqvist preservation theorem for this semantics. We show that every Sahlqvist sequent has a frame correspondent in first-order logic with fixed-point operators.