Full bispectra from primordial scalar and tensor perturbations in the   most general single-field inflation model
  We compute the full bispectra, namely both auto- and cross- bispectra, of primordial curvature and tensor perturbations in the most general single-field inflation model whose scalar and gravitational equations of motion are of second order. The formulae in the limits of k-inflation and potential-driven inflation are also given. These expressions are useful for estimating the full bispectra of temperature and polarization anisotropies of the cosmic microwave background radiation. 
Xian Gao, Tsutomu Kobayashi, Maresuke Shiraishi, Masahide Yamaguchi,   Jun'ichi Yokoyama, Shuichiro Yokoyama
astro-ph.CO gr-qc hep-ph hep-th