Cosmic shear of the microwave background: The curl diagnostic
Weak-lensing distortions of the cosmic-microwave-background (CMB) temperature and polarization patterns can reveal important clues to the intervening large-scale structure. The effect of lensing is to deflect the primary temperature and polarization signal to slightly different locations on the sky. Deflections due to density fluctuations, gradient-type for the gradient of the projected gravitational potential, give a direct measure of the mass distribution. Curl-type deflections can be induced by, for example, a primordial background of gravitational waves from inflation or by second-order effects related to lensing by density perturbations. Whereas gradient-type deflections are expected to dominate, we show that curl-type deflections can provide a useful test of systematics and serve to indicate the presence of confusing secondary and foreground non-Gaussian signals.
Additional Information© 2005 The American Physical Society. Received 25 February 2005; published 28 June 2005. M.K. thanks C. Vale and C. Hirata for useful discussions. This work was supported in part by NASA NAG5-11985 and DoE DE-FG03-92-ER40701 at Caltech and NSF AST-0349213 at Dartmouth.
Published - COOprd05.pdf