Skew monoidal structure on categories of algebras

Description

Invited talk for the Category Theory Seminar, University of Cambridge.

(joint work with M. Fiore)

There is a long tradition of constructing monoidal or closed structure on the category of algebras for a monad that is assumed to be commutative, monoidal, cartesian closed, or similar. In each case, one builds a tensor product classifying bilinear maps using a coequalizer. This approach, initiated by Linton’s description of the construction, has been studied by Kock, Guitart and others, while Seal has recently examined the monodial case in some detail. In this talk we explore these ideas for skew monoidal categories, viz. suitably directed versions of monoidal categories in which the structural maps are not assumed to be invertible. I will show that for a strong monad T on a skew monoidal category, the category of T-algebras acquires a skew monoidal structure with a tensor product classifying left-linear maps. I will then characterise the monoids for this left-linear monoidal structure as precisely the T-monoids of Fiore et al, and give two constructions for free monoids in skew monoidal categories.

Period	28 Nov 2017
Held at	University of Cambridge, United Kingdom