The subdominant curvaton

Abstract

We present a systematic study of the amplitude of theprimordial perturbation in curvaton models with self-interactions,treating both renormalizable and non-renormalizable interactions. Inparticular, we consider the possibility that the curvaton energydensity is subdominant at the time of the curvaton decay. We findthat large regions in the parameter space give rise to the observedamplitude of primordial perturbation even for non-renormalizablecurvaton potentials, for which the curvaton energy density dilutesfast. At the time of its decay, the curvaton energy density maytypically be subdominant by a relative factor of 10−3 and stillproduce the observed perturbation. Field dynamics turns out to behighly non-trivial, and for non-renormalizable potentials andcertain regions of the parameter space we observe a non-monotonousrelation between the final curvature perturbation and the initialcurvaton value. In those cases, the time evolution of the primordialperturbation also displays an oscillatory behaviour before thecurvaton decay.