Numerical evaluation of the three-point scalar-tensor cross-correlations
  and the tensor bi-spectrum
  Utilizing the Maldacena formalism and extending the earlier efforts to
compute the scalar bi-spectrum, we construct a numerical procedure to evaluate
the three-point scalar-tensor cross-correlations as well as the tensor
bi-spectrum in single field inflationary models involving the canonical scalar
field. We illustrate the accuracy of the adopted procedure by comparing the
numerical results with the analytical results that can be obtained in the
simpler cases of power law and slow roll inflation. We also carry out such a
comparison in the case of the Starobinsky model described by a linear potential
with a sudden change in the slope, which provides a non-trivial and interesting
(but, nevertheless, analytically tractable) scenario involving a brief period
of deviation from slow roll. We then utilize the code we have developed to
evaluate the three-point correlation functions of interest (and the
corresponding non-Gaussianity parameters that we introduce) for an arbitrary
triangular configuration of the wavenumbers in three different classes of
inflationary models which lead to features in the scalar power spectrum, as
have been recently considered by the Planck team. We also discuss the
contributions to the three-point functions during preheating in inflationary
models with a quadratic minimum. We conclude with a summary of the main results
we have obtained.
