CMB spectral distortions in generic two-field models

Abstract

We investigate the CMB μ distortion in models where two uncorrelated sources contribute to primordial perturbations. We parameterise each source by an amplitude, tilt, running and running of the running. We perform a detailed analysis of the distribution signal as function of the model parameters, highlighting the differences compared to single-source models. As a specific example, we also investigate the mixed inflaton-curvaton scenario. We find that the μ distortion could efficiently break degeneracies of curvaton parameters especially when combined with future sensitivity of probing the tensor-to-scalar ratio r. For example, assuming bounds μ < 0.5 × 10−8 and r<0.01, the curvaton contribution should either vanish or the curvaton should dominate primordial perturbations and its slow-roll parameter ηχ is constrained to the interval −0.007 < ηχ< 0.045.