Running spectral index from shooting-star moduli

Abstract

Abstract:We construct an inflationary model that is consistent with both large nonGaussianity and a running spectral index. The scenario of modulated inflation suggests that modulated perturbation can induce the curvature perturbation with a large nonGaussianity, even if the inflaton perturbation is negligible. Using this idea, we consider a multi-field extension of the modulated inflation scenario and examine the specific situation where different moduli are responsible for the perturbation at different scales. We suppose that the additional moduli (shooting-star moduli) is responsible for the curvature perturbation at the earlier inflationary epoch and it generates the fluctuation with n > 1 spectral index at this scale. After a while, another moduli (or inflaton) takes the place and generates the perturbation with n < 1. At the transition point the two fluctuations are comparable with each other. We show how the spectral index is affected by the transition induced by the shooting-star moduli.

Ambiguity in running spectral index with an extra light field during inflation

“…Also in refs. [34][35][36], it has been pointed out that such field might shift the spectral index and its running. Viewing those studies, we think that the idea of changing the scale dependence of the curvature perturbation using an additional dynamical field could have been known partly, although we could not find explicit calculation that can be used for solving the tension between BICEP2 and other experiments.…”

TheN-vaton

“…(A.17)Similarly, we can also calculate the total non-Gaussianity parameter f tot N L . Here we only give the result:f tot N L = β 2f nc N L + β(1 − β)f cross N L + (1 − β) 2f inf N L, N L is determined by concrete inflation models[54][55][56][57][58][59][60][61][62][63].…”