Characterization of metrizable Esakia spaces via some forbidden configurations

TL;DR

This paper characterizes metrizable Esakia spaces using forbidden configurations, providing a new way to identify countable Heyting algebras and exploring limitations in the uncountable case.

Contribution

It introduces a characterization of metrizable Esakia spaces via forbidden configurations, linking topological properties to algebraic structures.

Findings

Metrizable Esakia spaces can be characterized by three forbidden configurations.

This characterization applies to countable Heyting algebras.

The characterization does not extend to uncountable cases.

Abstract

By Priestley duality, each bounded distributive lattice is represented as the lattice of clopen upsets of a Priestley space, and by Esakia duality, each Heyting algebra is represented as the lattice of clopen upsets of an Esakia space. Esakia spaces are those Priestley spaces that satisfy the additional condition that the downset of each clopen is clopen. We show that in the metrizable case Esakia spaces can be singled out by forbidding three simple configurations. Since metrizability yields that the corresponding lattice of clopen upsets is countable, this provides a characterization of countable Heyting algebras. We show that this characterization no longer holds in the uncountable case. Our results have analogues for co-Heyting algebras and bi-Heyting algebras, and they easily generalize to the setting of p-algebras.