Perturbation spectrum after inflation

1. Feb 8, 2008

smallphi

The spectrum of perturbations at the end of inflation, which turns out to be flat and slightly red shifted, is calculated under the assumption that each perturbation mode crosses some initial time in the comoving coordinates with 'minimum energy allowed by the Heisenberg uncertainty principle'.

Does the spectrum change if the initial conditions of the modes are changed?

Isn't using the comoving coordinates in violation of the principle of general covariance in GR i. e. it singles out a preferred frame to calculate 'physical observables'?