Monoids up to coherent homotopy in two-level type theory


When defining a monoid structure on an arbitrary type in HoTT, one should require a multiplication that is not only homotopy-associative, but also has an infinite tower of higher homotopies. For example in dimension two one should have a condition similar to Mac Lane’s pentagon for monoidal categories. We call such a monoid a monoid up to coherent homotopy.
   The goal of my internship in Stockholm was to formalize them in Agda.
   It is well-known that infinite towers of homotopies are hard to handle in plain HoTT, so we postulate a variant of two-level type theory, with a strict equality and an interval type. Then we adapt the set-theoretical treatment of monoids up to coherent homotopy using operads as presented by Clemens Berger and Ieke Moerdijk. Our main results are
   (a) Monoids up to coherent homotopy are invariant under homotopy equivalence
   (b) Loop spaces are monoids up to coherent homotopy.
   In this talk I will present the classical theory of monoids up to coherent homotopy, and indicates how two-level type theory can be used to formalize it.

Apr 11, 2019
Deducteam seminar
Hugo Moeneclaey
Hugo Moeneclaey