Frontal operators in weak Heyting algebras

Abstract

In this paper we shall introduce the variety FWHA of frontal weak Heyting algebras as a generalization of the frontal Heyting algebras introduced by Leo Esakia in [10]. A frontal operator in a weak Heyting algebra A is an expansive operator τ preserving nite meets which also satis es the equation τ (a) ≤ b ∨ (b → a), for all a; b ∈ A. These operators were studied from an algebraic, logical and topological point of view by Leo Esakia in [10]. We will study frontal operators in weak Heyting algebras and we will consider two examples of them. We will give a Priestley duality for the category of frontal weak Heyting algebras in terms of relational spaces ⟨X;≤; T;R⟩ where ⟨X;≤; T⟩ is a WH- space [6], and R is an additional binary relation used to interpret the modal operator. We will also study the WH-algebras with successor and the WH-algebras with gamma. For these varieties we will give two topological dualities. The rst one is based on the representation given for the frontal weak Heyting algebras. The second one is based on certain particular classes of WH-spaces.