Abstract

Future lensing surveys aim at observing almost the whole sky. They will measure lensing correlations at very large scales. At those scales, new relativistic effects will come into play and open the way to new type of studies. In this talk, I will present a fully relativistic calculation of weak gravitational lensing up to second order in the gravitational potential. First, I will show that the convergence part of weak lensing contains new effects that are neglected at small scales. I will show that one of these contributions, generated by peculiar velocities of galaxies, becomes important at large scales. At small redshifts, it has an observable impact on the convergence power spectrum. Then I will present a calculation of the shear part of weak lensing up to second order. I will show that at large scales various non-linear couplings appear that can potentially provide new tests of gravity.