Parametric amplification of metric fluctuations during reheating in two field models - art. no. 083502

We study the parametric amplification of super-Hubble-scale scalar metric f luctuations at the end of inflation in some specific two-field models of in flation, a class of which is motivated by hybrid inflation We demonstrate t hat there can indeed be a large growth of fluctuations due to parametric re sonance and that this effect is not taken into account by the conventional theory of isocurvature perturbations. Scalar field interactions play a cruc ial role in this analysis. We discuss the conditions under which there can be nontrivial parametric resonance effects on large scales.