Curvaton scenarios with inflaton decays into curvatons
  We consider the possible decay of the inflaton into curvaton particles during
reheating and analyse its effect on curvaton scenarios. Typical decay curvatons
are initially relativistic then become non-relativistic, changing the
background history of the Universe. We show that this change to the background
is the only way in which observational predictions of the scenario are
modified. Moreover, once the required amplitude of perturbations is fixed by
observation there are no signatures of such decays in other cosmological
observables. The decay curvatons can prevent the Universe from becoming
dominated by the curvaton condensate, making it impossible to match
observations in parts of parameter space. This constrains the branching ratio
of the inflaton to curvaton to be less than of order $0.1$ typically. If the
branching ratio is below about $10^{-4}$ it has negligible impact on the model
parameter space and can be ignored.
