Multi-field fermionic preheating

Fermion creation during preheating in the presence of multiple scalar fields exhibits a range of interesting behaviour. We present non-perturbative analysis of fermion production over a 6-dimensional parameter space in an expanding background paying particular attention to the interplay between instant preheating (χ-ψ) and direct fermion preheating (φ-ψ). In the broad resonance regime we find that instant fermion production is sensitive to suppression of long wavelength χ modes during inflation. Further, the standard scenario of resonant fermionic preheating through inflaton decay can be significantly modified by the χ-ψ coupling, and may even lead to a decrease in the number of fermions produced. We explicitly include the effects of metric perturbations and demonstrate that they are important at small coupling but not at strong coupling, due to the rapid saturation of the Pauli bound.