Bi-intermediate logics of trees and co-trees

N. Bezhanishvili, M. Martins, T. Moraschini

A bi-Heyting algebra validates the Gödel-Dummett axiom $(p\to q)\vee (q\to p)$ iff the poset of its prime filters is a disjoint union of co-trees (i.e., order duals of trees). Bi-H…