Non-Gaussianities in the cosmological perturbation spectrum due to primordial anisotropy II

Abstract

We continue to investigate possible signatures of a pre-inflationary\nanisotropic phase in two-point and three point correlation functions of the\ncurvature perturbation for high-momentum modes which exit the horizon well\nafter isotropization. The late time dynamics of these modes is characterized by\na non-Bunch Davies vacuum state which encodes all the information about initial\nanisotropy in the background space-time. We observe that, unlike the non-planar\nmomenta, there exist regimes of planar momenta for which scale invariance of\nthe power spectrum is strongly broken. This regime of planar momenta gives rise\nto enhanced non-Gaussianity in certain squeezed triangle configurations,\nalthough the enhancement of the $f_{NL}$ parameter is limited by the breakdown\nof linear perturbation theory at "exact planarity". Finally, we demonstrate\nthat for the range of planar modes for which scale invariance of the power\nspectrum is preserved, non-Gaussianity in the curvature perturbation spectrum\nis naturally constrained to be extremely small.\n