Quantifying the 'naturalness' of the curvaton model
  We investigate the probability of obtaining an observable curvature
perturbation, using as an example the minimal curvaton-higgs (MCH) model. We
determine 'probably observable' and 'probably excluded' regions of parameter
space assuming generic initial conditions and applying a stochastic approach
for the curvaton's evolution during inflation. Inflation is assumed to last
longer than the N_{obs} = 55 observable e-folds, and the total number of
e-folds of inflation determines the particular ranges of parameters that are
probable. For the MCH model, these 'probably observable' regions always lie
within the range 8 x 10^4 GeV < m_\sigma\ < 2 x 10^7 GeV, where m_\sigma\ is
the curvaton mass, and the Hubble scale at horizon exit is chosen as H_* =
10^{10} GeV. Because the 'probably observable' region depends on the total
duration of inflation, information on parameters in the Lagrangian from
particle physics and from precision CMB observables can therefore provide
information about the total duration of inflation, not just the last N_{obs}
e-folds. This method could also be applied to any model that contains
additional scalar fields to determine the probability that these scalar fields
contribute to the curvature perturbation.
