Direct search for features in the primordial bispectrum

TL;DR

This paper investigates features in the primordial bispectrum by linking it to the reconstructed primordial power spectrum from Planck data, finding marginal deviations in specific configurations that suggest potential non-standard features.

Contribution

It provides a model-independent method to express the bispectrum in terms of the power spectrum and its derivatives, applied to observational data to identify possible features.

Findings

Marginal 2sigma deviations in the squeezed limit at specific scales.

Bispectrum consistent with featureless model in equilateral configuration.

Method links bispectrum directly to reconstructed power spectrum.

Abstract

We study features in the bispectrum of the primordial curvature perturbation correlated with the reconstructed primordial power spectrum from the observed cosmic microwave background temperature data. We first show how the bispectrum can be completely specified in terms of the power spectrum and its first two derivatives, valid for any configuration of interest. Then using a model-independent reconstruction of the primordial power spectrum from the Planck angular power spectrum of temperature anisotropies, we compute the bispectrum in different triangular configurations. We find that in the squeezed limit at k ~ 0.06/Mpc and k ~ 0.014/Mpc there are marginal 2sigma deviations from the standard featureless bispectrum, which meanwhile is consistent with the reconstructed bispectrum in the equilateral configuration.