Violation of the rotational invariance in the CMB bispectrum

Abstract

We investigate a statistical anisotropy on the Cosmic Microwave Background (CMB) bispectrum, which can be generated from the primordial non-Gaussianity induced by quantum uctuations of a vector field. We find new congurations in the multipole space of the CMB bispectrum given by ℓ1 = ℓ2+ℓ3+2/ℓ2 - ℓ3 - 2 and their permuta- Tions, which violate the rotational invariance, such as an off-diagonal conguration in the CMB power spectrum. We also find that in a model presented by Yokoyama and Soda (2008), the amplitude of the statistically anisotropic bispectrum in the above configurations becomes as large as that in other configurations such as ℓ1 = ℓ2 + ℓ3. As a result, it might be possible to detect these contributions in future experiments, which would give us novel information about the physics of the early Universe.