We derive the expressions for the one-loop corrections in cosmological, Eulerian, perturbation theory to the matter bispectrum and to the galaxy bispectrum, assuming local galaxy bias, in the presence of non-Gaussian initial conditions. We compute them explicitly for the particular case of nonvanishing initial bispectrum and trispectrum in the local model and for a nonvanishing initial bispectrum alone for the equilateral model of primordial non-Gaussianity. While the primordial contribution to the matter bispectrum for values compatible with cosmic microwave background observations is dominant over the component due to gravitational instability at large scales, one-loop perturbative corrections due to non-Gaussian initial conditions correspond to just a few percent of the gravity-induced bispectrum at mildly nonlinear scales, similar to what happens for the matter power spectrum. However, in the perturbative expansion for the galaxy bispectrum, one-loop diagrams arising from nonlinear 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.

• Received 16 June 2009

DOI:https://doi.org/10.1103/PhysRevD.80.123002