Ordered semirings and subadditive morphisms

Abstract

An ordered semiring is a commutative semiring equipped with a compatible preorder. Ordered semirings generalise both distributive lattices and commutative rings, and provide a convenient framework to unify certain aspects of lattice theory and ring theory. The ideals of an ordered semiring $A$ form a commutative integral quantale $\mathrm{Idl}(A)$, and similarly, the radical ideals of $A$ form a (spatial) frame $\mathrm{Rad}(A)$. We characterise $\mathrm{Idl}$ and $\mathrm{Rad}$ as the left adjoints of the (non-full) inclusion functors from the categories of commutative integral quantales and of frames, respectively, to that of ordered semirings and subadditive morphisms between them. The (sober) topological space $\mathrm{pt}(\mathrm{Rad}(A))$ corresponding to $\mathrm{Rad}(A)$ is homeomorphic to the space $\mathrm{Spec}(A)$ of prime ideals of $A$.