Gravitational time delay effects on cosmic microwave background anisotropies - art. no. 023504

We study the effect of gravitational time delay on the power spectra and bi spectra of the cosmic microwave background (CMB) temperature and polarizati on anisotropies. The time delay effect modulates the spatial surface at rec ombination on which temperature anisotropies are observed, typically by sim ilar to1 Mpc. While this is a relatively large shift, its observable effect s in the temperature and polarization fields are suppressed by geometric co nsiderations. The leading order effect is from its correlation with the clo sely related gravitational lensing effect. The change to the temperature-po larization cross power spectrum is of order 0.1% and is hence comparable to the cosmic variance for the power in the multipoles around l similar to 10 00. While unlikely to be extracted from the data in its own right, its omis sion in modeling would produce a systematic error comparable to this limiti ng statistical error and, in principle, is relevant for future high precisi on experiments. Contributions to the bispectra result mainly from correlati ons with the Sachs-Wolfe effect and may safely be neglected in a low densit y universe.