How the curvaton scenario, modulated reheating and an inhomogeneous end
  of inflation are related
  In this paper we analyse three models of the early universe, for which the
respective mechanisms for generating the curvature perturbation are considered
disparate. We find that in fact the mechanisms are very similar, and hence
explain why they give rise to a large non-gaussianity. We show that the
mechanism for generating the primordial curvature perturbation, and hence the
observable non-gaussianity, is similar in both the Curvaton and Modulated
Reheating models. In both cases the model can be written in terms of an energy
transfer between the constituting fluids. We then show that this is also true
for the mechanism of generating the curvature perturbation by symmetry breaking
the end of inflation. We then relate this to the non-gaussian contribution to
the curvature perturbation and find that it is inversely proportional to the
efficiency with which the curvature perturbation is transferred between the
fluids. For the first time, we generalise models of modulated reheating to
allow for a non-linear energy transfer rate.
