Computable isomorphisms of distributive lattices

Abstract

© Springer Nature Switzerland AG 2019. A standard tool for the classifying computability-theoretic complexity of equivalence relations is provided by computable reducibility. This gives rise to a rich degree-structure which has been extensively studied in the literature. In this paper, we show that equivalence relations, which are complete for computable reducibility in various levels of the hyperarithmetical hierarchy, arise in a natural way in computable structure theory. We prove that for any computable successor ordinal α, the relation of (formula presented) isomorphism for computable distributive lattices is (formula presented) complete. We obtain similar results for Heyting algebras, undirected graphs, and uniformly discrete metric spaces.