Entropy Production in a Lepton-Photon Universe

Understand

We look at the entropy production during the lepton era in the early Universe by using a model where we exclude all particles except the leptons and photons.

• We assume a temperature dependent viscosity as calculated recently by one of us (Husdal 2016) with use of relativistic kinetic theory.
• We consider only the bulk viscosity, the shear viscosity being omitted because of spatial isotropy.
• The rate of entropy production is highest just before the neutrinos decouple.