2PI simulations in expanding backgrounds: Doing it anyway!

I set out the 2PI formalism for quantum fields in a Friedmann-Robertson-Walker Universe. I show how one can solve self-consistently for the quantum field evolution and the evolution of the cosmological scale factor, using a renormalised semi-classical Friedmann equation. In a 2PI coupling expansion truncated at O(λ2), I perform sample calculations demonstrating kinetic and chemical equilibration in this context.