The intrinsic bispectrum of the Cosmic Microwave Background
  We develop a new, efficient code for solving the second-order
Einstein-Boltzmann equations, and use it to estimate the intrinsic CMB
non-Gaussianity arising from the non-linear evolution of density perturbations.
The full calculation involves contributions from recombination and less
tractable contributions from terms integrated along the line of sight. We
investigate the bias that this intrinsic bispectrum implies for searches of
primordial non-Gaussianity. We find that the inclusion or omission of certain
line of sight terms can make a large impact. When including all physical
effects but lensing and time-delay, we find that the local-type f_nl would be
biased by f_nl ~ 0.5, below the expected sensitivity of the Planck satellite.
The speed of our code allows us to confirm the robustness of our results with
respect to a number of numerical parameters.
