Primordial Stochastic Gravitational Wave Background Anisotropies: in-in Formalization and Applications

Understand

Primordial non-Gaussianities of the scalar(tensor)-tensor-tensor type supporting a non-trivial squeezed component are known to induce anisotropies in the stochastic gravitational wave background.

• We derive the explicit form of such anisotropies by making use, for the first time in this context, of the in-in formalism for cosmological correlation functions.
• After illustrating the general method and using it for the minimal single-field slow-roll case, we apply it to multi-field models, providing both a tree-level and a one-loop example.
• First, we make contact with previous results on anisotropies due to the presence of an extra spin-2 field during inflation.