Polycategories via pseudo-distributive laws

Abstract

In this paper, we give a novel abstract description of Szabo's polycategories. We use the theory of double clubs -- a generalisation of Kelly's theory of clubs to `pseudo' (or `weak') double categories -- to construct a pseudo-distributive law of the free symmetric strict monoidal category pseudocomonad on Mod over itself qua pseudomonad, and show that monads in the `two-sided Kleisli bicategory' of this pseudo-distributive law are precisely symmetric polycategories.