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Colloquium by John Peacock (University of Edinburgh)

Gravitational lensing of the Cosmic Microwave Background:flux conservation and growth of inhomogeneities


Gravitational lensing probes both the amplitude and evolution of cosmological metric fluctuations, plus the distance-redshift relation. But relativists have claimed that lensing also causes an average non-Newtonian "back-reaction" effect, which alters the effective distance to the CMB last-scattering surface, causing substantial error in the cosmological parameters we infer. The first part of this talk discusses this issue from the point of view of flux conservation theorems due to Weinberg and to Kibble & Lieu. The second part of the talk presents some new results on cross-correlation between galaxy surveys (based on WISE & SuperCOSMOS) and CMB lensing data. These yield interesting measurements of the evolution of cosmological perturbations at redshift z<0.5.

Time: September 7, 2016, 2:30 pm

Venue: A601, NAOC