1-loop Perturbative Corrections to the Matter and Galaxy Bispectrum with non-Gaussian Initial Conditions

TL;DR

This paper calculates 1-loop perturbative corrections to matter and galaxy bispectra considering non-Gaussian initial conditions, revealing their relative importance at different scales and configurations in cosmology.

Contribution

It provides explicit formulas for 1-loop corrections to matter and galaxy bispectra with non-Gaussian initial conditions, including local and equilateral models.

Findings

Primordial non-Gaussianity dominates at large scales for the matter bispectrum.

1-loop corrections from non-Gaussian initial conditions are a few percent at mildly non-linear scales.

Non-linear bias effects significantly impact the galaxy bispectrum at large scales.

Abstract

We derive the expressions for the 1-loop corrections in cosmological, Eulerian, perturbation theory to the matter bispectrum and to the galaxy bispectrum, assuming local galaxy bias, in presence of non-Gaussian initial conditions. We compute them explicitly for the particular case of non-vanishing initial bispectrum and trispectrum in the local model and for a non-vanishing initial bispectrum alone for the equilateral model of primordial non-Gaussianity. While the primordial contribution to the matter bispectrum for values compatible with CMB observations is dominant over the component due to gravitational instability at large scales, 1-loop perturbative corrections due to non-Gaussian initial conditions correspond to just a few percent of the gravity-induced bispectrum at mildly non-linear scales, similarly to what happens for the matter power spectrum. However, in the perturbative expansion for the galaxy bispectrum, 1-loop diagrams arising from non-linear bias are responsible for significant large-scale contributions, indeed exceeding the primordial component, both for the local and equilateral model. We study the peculiar dependence on scale and on the shape of the triangular configurations of such additional terms, similar in their origin to the large-scale corrections to the halo and galaxy power spectra that raised significant interest in the recent literature.