Primordial density fluctuations

For potentials with an almost flat section, a general expression is derived for the time evolution of energy density correlations inside the horizon, for an arbitrary quantum state. The particular case of the de Sitter invariant vacuum is studied in detail. At the horizon, an energy contrast is found to be one order of magnitude larger than usual estimates, based on the Hawking temperature. The source for this contribution are quantum fluctuations at short distances. The small correction due to the time dependence of the Hubble constant is also estimated. (author)