Primordial non-gaussianities of gravitational waves in the most general single-field inflation model with second-order field equations

Xian Gao (1, 2, 3) , Tsutomu Kobayashi (4) , Masahide Yamaguchi (5) , Jun'Ichi Yokoyama (6)

1 IAP - Institut d'Astrophysique de Paris
2 APC (UMR_7164) - AstroParticule et Cosmologie
3 LPTENS - Laboratoire de Physique Théorique de l'ENS [École Normale Supérieure]
4 Kyoto University
5 TITECH - Tokyo Institute of Technology [Tokyo]
6 RESCEU - Research Center for the Early Universe

We completely clarify the feature of primordial non-Gaussianities of tensor perturbations in the most general single-field inflation model with second-order field equations. It is shown that the most general cubic action for the tensor perturbation h_ij is composed only of two contributions, one with two spacial derivatives and the other with one time derivative on each h_ij. The former is essentially identical to the cubic term that appears in Einstein gravity and predicts a squeezed shape, while the latter newly appears in the presence of the kinetic coupling to the Einstein tensor and predicts an equilateral shape. Thus, only two shapes appear in the graviton bispectrum of the most general single-field inflation model, which could open a new clue to the identification of inflationary gravitational waves in observations of cosmic microwave background anisotropies as well as direct detection experiments.

Keywords: Particle-theory and field-theory models of the early Universe; Gravitational-wave astrophysics; General Relativity and Quantum Cosmology; High Energy Physics - Phenomenology; High Energy Physics - Theory

Domains: Sciences of the Universe [physics]

Xian Gao, Tsutomu Kobayashi, Masahide Yamaguchi, Jun'Ichi Yokoyama. Primordial non-gaussianities of gravitational waves in the most general single-field inflation model with second-order field equations. Physical Review Letters, 2011, 107, pp.211301. ⟨10.1103/PhysRevLett.107.211301⟩. ⟨insu-03645846⟩