We offer a new approach to analyse the appearance of features in the primordial bispectrum that justifies the search of oscillating patterns modulated by orthogonal and local templates in the cosmic microwave background data. By studying the dynamics of the primordial curvature perturbation during inflation, we find that the couplings parametrising cubic self-interactions, responsible for features, can be expressed as functions of the bispectrum along specific directions in momentum space. As a result, we find a general expression describing departures from scale invariance in the bispectrum telling us how these appear modulated by different classes of shapes. On one hand, this result allows us to relate features appearing in different shapes in a unique way, such that if they are observed in a particular shape, they have to spread to others obeying certain rules. On the other hand, it serves as a tool to produce new templates of features in the bispectrum modulated by shapes that so far have not been considered to analyse data.
J. Gong, G. Palma and S. Sypsas
Wed, 1 Mar 17
Comments: 16 pages, 3 figures, 1 table