Varieties of ordered algebras as categories

Abstract

A variety is a category of ordered (finitary) algebras presented by inequations between terms. We characterize categories enriched over the category of posets which are equivalent to a variety. This is quite analogous to Lawvere's classical characterization of varieties of ordinary algebras. We also prove that varieties of ordered algebras are precisely the free completions of duals of discrete Lawvere theories under sifted colimits.

revised version, 29 pages