CMB B-mode auto-bispectrum produced by primordial gravitational waves

Understand

Gravitational waves from inflation induce polarization patterns in the cosmic microwave background (CMB).

• It is known that there are only two types of non-Gaussianities of the gravitaional waves in the most general scalar field theories having second-order field equations.
• One originates from the inherent non-Gaussianity in general relativity, and the other from a derivative coupling between the Einstein tensor and a kinetic term of the scalar field.
• We calculate polarization bispectra induced by these non-Gaussianities by transforming them into separable forms by virtue of the Laplace transformation.