Effect of lensing non-Gaussianity on the CMB power spectra
  Observed CMB anisotropies are lensed, and the lensed power spectra can be
calculated accurately assuming the lensing deflections are Gaussian. However,
the lensing deflections are actually slightly non-Gaussian due to both
non-linear large-scale structure growth and post-Born corrections. We calculate
the leading correction to the lensed CMB power spectra from the
non-Gaussianity, which is determined by the lensing bispectrum. The
lowest-order result gives $\sim 0.3\%$ corrections to the BB and EE
polarization spectra on small-scales, however we show that the effect on EE is
reduced by about a factor of two by higher-order Gaussian lensing smoothing,
rendering the total effect safely negligible for the foreseeable future. We
give a simple analytic model for the signal expected from skewness of the
large-scale lensing field; the effect is similar to a net demagnification and
hence a small change in acoustic scale (and therefore out of phase with the
dominant lensing smoothing that predominantly affects the peaks and troughs of
the power spectrum).
