The running curvaton

In this paper,we propose a homogeneous curvaton mechanism that operates during the preheating process and in which the effective mass is running(i.e.,its potential consists of a coupling term and an exponential term whose contribution is subdominant thereto).This mechanism can be classified into either narrow resonance or broad resonance cases,with the spectral index of the curvaton consituting the deciding criteria.The inflationary potential is that of chaotic inflation(i.e.,a quadratic potential),which could result in a smooth transition into the preheating process.The entropy perturbations are converted into curvature perturbations,which we validate using theδN formalism.By neglecting the exponential term's contribution to the curvaton potential,we calculate the power spectrum Pζand the nonlinear non-Gaussian parameter fNL.Our calculations analytically show that these two observables are independent of the inflaton potential.Finally,when the curvaton decays(and the inflaton field vanishes),the exponential potential approaches a constant value similar to that of the cosmological constant,which may play the role of dark energy.