Gauge-invariant metric perturbations during reheating

The possible amplification of gauge-invariant metric fluctuations in the infrared sector is very important during the reheating stage of inflation. In this stage the inflation field oscillates around the minimum of the scalar potential. The evolution for the super Hubble scales gauge-invariant metric fluctuations can be studied by means of the Bardeen parameter. For a massive scalar field with potential V(Φc)=m2/2Φ2c + Λ with nonzero cosmological constant I find that (in the reheating regime and for super Hubble scales) the Sasaki-Mukhanov parameter oscillates with amplitude constant such that there is not amplification of Q during reheating