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 $\fnl\simeq 0$ while $\gnl$ is non-zero. In the
case of a curvaton with mass $m\sim {\cal O}(1)$ TeV we show that one cannot
ignore non-quadratic terms in the potential, and that only a self-interaction
of the type $V_{\rm int}=\sigma^8/M^4$ 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.
