O-V-S-Z and friends: Non-Gaussianity from inhomogeneous reionization
  We calculate the cosmic microwave background (CMB) bispectrum due to
inhomogeneous reionization. We calculate all the terms that can contribute to
the bispectrum that are products of first order terms on all scales in
conformal Newtonian gauge. We also correctly account for the de-correlation
between the matter density and initial conditions using perturbation theory up
to third order. We find that the bispectrum is of local type as expected. For a
reasonable model of reionization, in which the Universe is completely ionized
by redshift z_{ri} ~ 8 with optical depth to the last scattering surface
\tau_0=0.087 the signal to noise for detection of the CMB temperature
bispectrum is S/N ~ 0.1 and confusion in the estimation of primordial
non-Gaussianity is f_{NL} ~ -0.1. For an extreme model with z_{ri} ~ 12.5,
\tau_0=0.14 we get S/N ~ 0.5 and f_{NL} ~ -0.2.
