Mixed inflaton and curvaton perturbations

A recent variant of the inflationary paradigm is that the primordial curvature perturbations come from quantum fluctuations of a scalar field, subdominant and effectively massless during inflation, called the curvaton, instead of the fluctuations of the inflaton field. We consider the situation where the primordial curvature perturbations generated by the quantum fluctuations of an inflaton and of a curvaton field are of the same order of magnitude. We compute the total curvature perturbation and its spectrum in this case and we discuss the observational consequences.