Quantum theory of fermion preheating

We show that quantum effects dramatically influence the production of fermions during preheating after inflation in the early universe. So far, nonequilibrium fermion production has been mainly investigated using the Dirac equation with coupling to a homogeneous classical inflaton field. We extend this analysis by taking into account quantum corrections including scattering and decay processes, as well as off-shell and memory effects. This is done by using two-particle irreducible (2PI) effective action techniques, which we compare to results from lattice simulations.