Enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities (2305.07076v2)

Abstract: Lawvere's algebraic theories, or Lawvere theories, underpin a categorical approach to general algebra, and Lawvere's adjunction between semantics and algebraic structure leads to an equivalence between Lawvere theories and finitary monads on the category of sets. Several authors have transported these ideas to a variety of settings, including contexts of category theory enriched in a symmetric monoidal closed category. In this paper, we develop a general axiomatic framework for enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities. Not only do we establish a simultaneous generalization of the monad-theory equivalences previously developed in the settings of Lawvere (1963), Linton (1966), Dubuc (1970), Borceux-Day (1980), Power (1999), Nishizawa-Power (2009), Lack-Rosick\'y (2011), Lucyshyn-Wright (2016), and Bourke-Garner (2019), but also we establish a structure-semantics theorem that generalizes those given in the first four of these works while applying also to the remaining five, for which such a result has not previously been developed. Furthermore, we employ our axiomatic framework to establish broad new classes of examples of enriched monad-theory equivalences and structure-semantics adjunctions for subcategories of arities enriched in locally bounded closed categories, including various convenient closed categories that are relevant in topology and analysis and need not be locally presentable.