Adiabatic Gravitational Perturbation During Reheating
W. B. Lin, X. H. Meng, X. M. Zhang
TL;DR
Problem addressed: whether parametric resonance during reheating amplifies gravitational perturbations in single-field inflation. Approach: derive evolution equations for the perturbations via Sasaki-Mukhanov variables and analyze the super-horizon limit, complemented by numerical experiments. Findings: for general single-field potentials, the Bardeen parameter zeta remains constant on super-horizon scales during reheating, indicating no additional growth. Implication: supports the robustness of standard adiabatic perturbation predictions through reheating; amplification may only occur in multi-field setups, which require further study.
Abstract
We study the possibilities of parametric amplification of the gravitational perturbation during reheating in single-field inflation models. Our result shows that there is no additional growth of the super-horizon modes beyond the usual predictions.