Multi-field fermionic preheating

Fermion creation during preheating in the presence of multiple scalar field s exhibits a range of interesting behaviour. We present non-perturbative an alysis of fermion production over a 6-dimensional parameter space in an exp anding background paying particular attention to the interplay between inst ant preheating (chi-psi) and direct fermion preheating (phi-psi). In the br oad resonance regime we find that instant fermion production is sensitive t o suppression of long wavelength chi modes during inflation. Further, the s tandard scenario of resonant fermionic preheating through inflaton decay ca n be significantly modified by the chi-psi coupling, and may even lead to a decrease in the number of fermions produced. We explicitly include the eff ects of metric perturbations and demonstrate that they are important at sma ll coupling but not at strong coupling, due to the rapid saturation of the Pauli bound.