Shapes and features of the primordial bispectrum

Abstract

If time-dependent disruptions from slow-roll occur during inflation, the correlation functions of the primordial curvature perturbation should have scale-dependent features, a case which is marginally supported from the cosmic microwave background (CMB) data. We offer a new approach to analyze the appearance of such features in the primordial bispectrum that yields new consistency relations and justifies the search of oscillating patterns modulated by orthogonal and local templates. Under the assumption of sharp features, we find that the cubic couplings of the curvature perturbation can be expressed in terms of the bispectrum in two specific momentum configurations, for example local and equilateral. This allows us to derive consistency relations among different bispectrum shapes, which in principle could be tested in future CMB surveys. Furthermore, based on the form of the consistency relations, we construct new two-parameter templates for features that include all the known shapes.

(v1) 16 pages, 3 figures, 1 table; (v2) minor clarifications including updated abstract, to appear in Journal of Cosmology and Astroparticle Physics

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Cited by in corpus (5)

• Constraints on inflation with LSS surveys: features in the primordial power spectrum
• Complex dimensions and their observability
• Lensing anomaly and oscillations in the primordial power spectrum
• Degeneracy in the spectrum and bispectrum among featured inflaton potentials
• Cross-tests of CMB features in the primordial spectra