http://arxiv.org/abs/1812.00861
Weak lensing will play an important role in future cosmological surveys, including e.g. Euclid and the Square Kilometre Array. Sufficiently accurate theoretical predictions are important for correctly interpreting these surveys and hence for extracting correct cosmological parameter estimations. We quantify for the first time in a relativistic setting how many post-Born and lens-lens coupling corrections are required for sub-percent accuracy of the theoretical weak lensing convergence and distance-redshift relation for z<2 (the primary weak lensing range for Euclid and SKA). We do this by randomly ray-tracing through a fully relativistic exact solution of the Einstein Field Equations which consists of randomly packed mass-compensated under-densities of realistic amplitudes. We find that one needs to include lens-lens coupling terms and post-Born corrections at least up to second and third order respectively for sub-percent accuracy of the convergence and angular diameter distance d_A. We find that, out of the random lines of sight studied, post-Born corrections can be as large as 70% of the total correction to the area distance. We also provide a simplified operator formalism for calculating the leading corrections to these quantities to arbitrary order.
S. Koksbang and C. Clarkson
Tue, 4 Dec 18
34/78
Comments: 5 pages, 5 figures
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