The Self-Interacting Curvaton

The evolution of the curvature perturbation is highly non-trivial for curvaton models with self-interactions and is very sensitive to the parameter values. The final perturbation depends also on the curvaton decay rate Gamma. As a consequence, non-gaussianities can be greatly different from the purely quadratic case, even if the deviation is very small. Here we consider a class of polynomial curvaton potentials and discuss the dynamical behavior of the curvature perturbation. We point out that, for example, it is possible that the non-gaussianity parameter f(NL) similar or equal to 0 while g(NL) is non-zero. In the case of a curvaton with mass m similar to O(1) TeV we show that one cannot ignore non-quadratic terms in the potential, and that only a self-interaction of the type V-int = sigma(8)/M-4 is consistent with various theoretical and observational constraints. Moreover, the curvaton decay rate should then be in the range Gamma = 10(-15) - 10(-17) GeV.