The Quantum Phase of Inflation
  Inflation models can have an early phase of inflation where the evolution of
the inflaton is driven by quantum fluctuations before entering the phase driven
by the slope of the scalar field potential. For a Coleman-Weinberg potential
this quantum phase lasts 10^{7-8} e-foldings. A long period of fluctuation
driven growth of the inflation field can possibly take the inflaton past phi_*,
the value of the field where our current horizon scale crosses the horizon;
alternatively, even if the field does not cross phi_*, the inflaton could have
high kinetic energy at the end of this phase. Therefore we study these issues
in the context of different models of inflation. In scenarios where
cosmological relevant scales leave during the quantum phase we obtain large
curvature perturbations of O(10). We also apply our results to quadratic
curvaton models and to quintessence models. In curvaton models we find that
inflation must last longer than required to solve the horizon problem, that the
curvaton models are incompatible with small field inflation models and that
there may be too large non-gaussianity. A new phase of thermal fluctuation
driven inflation is proposed, in which during inflation the inflaton evolution
is governed by fluctuations from a sustained thermal radiation bath rather than
by a scalar field potential.
