Full-sky weak lensing: a nonlinear post-Friedmann treatment

Understand

We present a full-sky derivation of weak lensing observables in the Post-Friedmann (PF) formalism.

• Weak lensing has the characteristic of mixing small scales and large scales since it is affected by inhomogeneities integrated along the photon trajectory.
• With the PF formalism, we develop a modelling of lensing observables which encompasses both leading order relativistic effects and effects that are due to the fully non-linear matter distribution at small scales.
• We derive the reduced shear, convergence and rotation up to order $1/c^4$ in the PF approximation, accounting for scalar, vector and tensor perturbations, as well as galaxies' peculiar velocities.