Modulated preheating and isocurvature perturbations
  We consider a model of preheating where the coupling of the inflaton to the
preheat field is modulated by an additional scalar field which is light during
inflation. We establish that such a model produces the observed curvature
perturbation analogously to the modulated reheating scenario. The contribution
of modulated preheating to the power spectrum and to non-Gaussianity can
however be significantly larger compared to modulated perturbative reheating.
We also consider the implications of the current constraints on isocurvature
perturbations in case where the modulating field is responsible for cold dark
matter. We find that existing bounds on CDM isocurvature perturbations imply
that modulated preheating is unlikely to give a dominant contribution to the
curvature perturbation and that the same bounds suggest important constraints
on non-Gaussianity and the amount of primordial gravitational waves.
