Post-inflationary Reheating

We study the two field model for reheating based on the scalar inflaton field, φ, and its interaction with another scalar field, χ, through a Lagrangian term 1 2 gχφ,much investigated for parametric resonance or preheating. Attention is particularly on the quantum excitations of the inflaton field and the metric with a smooth transition from quantum to classical stochastic states, and with reheating followed right through from a specific inflation model to a state including a relativistic (radiation) fluid. The excitations of the metric (but not the inflaton or χ) are treated perturbatively and the validity of this approach is assessed. For this model our work points to the possibility of ζ (the curvature associated parameter for observed cosmic microwave background radiation anisotropies) changing significantly during reheating with parametric resonance.