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We analyse the situation where the primordial curvature perturbations areproduced by the joint effects of an inflaton field and two curvaton fields. Wepresent general equations which allow the reader to obtain f_NL for severaldifferent scenarios which differ in the order in which fields decay intoradiation after inflation. In order to investigate the physics of theseequations we analyse some simplified situations where the fields are harmonicand both curvatons are frozen at the same expectation value during inflation.We find quite complex behaviour - for a given situation where the inflatoncontributes a fixed amount to the total curvature perturbation there aresituations where f_NL is maximised if both curvatons share equally incontributing the rest and situations where f_NL is maximised if only one of thetwo curvatons contributes the rest. We are unable therefore to make anycompletely general extrapolations about the expected non-gaussianity from Ncurvatons. We find that as the curvaton contribution to the overallperturbation is gradually increased, f_NL rises to a maximum before fallingagain and that a given f_NL can correspond to many different parameter sets forthe two curvatons.

Mixed perturbations from an Inflaton and Two Curvatons - towards understanding non-gaussianity in more complicated curvaton scenarios