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Non-Gaussian Fingerprints of Self-Interacting Curvaton

We investigate non-Gaussianities in self-interacting curvaton models treating both renormalizable and non-renormalizable polynomial interactions. We scan the parameter space systematically and compute numerically the non-linearity parameters f_NL and g_NL. We find that even in the interaction dominated regime there are large regions consistent with current observable bounds. Whenever the interactions dominate, we discover significant deviations from the relations f_NL ~ 1/r_decay and g_NL ~ 1/r_decay valid for quadratic curvaton potentials, where r_decay measures the curvaton contribution to the total energy density at the time of its decay. Even if r_decay << 1, there always exists regions with f_NL ~ 0 since the sign of f_NL oscillates as a function of the parameters. While g_NL can also change sign, typically g_NL is non-zero in the low-f_NL regions. Hence, for some parameters the non-Gaussian statistics is dominated by g_NL rather than by f_NL. Due to self-interactions, both the relative signs of f_NL and g_NL and the functional relation between them is typically modified from the quadratic case, offering a possible experimental test of the curvaton interactions.