Large-scale weak lensing convergence in nonlinear general relativity

TL;DR

This study uses nonlinear general relativity and numerical simulations to evaluate weak lensing convergence, confirming the relevance of Doppler lensing at low redshifts and assessing the accuracy of linear perturbation theory across scales.

Contribution

It provides the first end-to-end nonlinear relativistic analysis of weak lensing convergence, comparing it with perturbation theory for large-scale structures.

Findings

Linear theory predicts convergence within 3-30% of nonlinear results.

Smaller angular scales are better matched by linear theory.

Discrepancies are mostly below cosmic variance levels.

Abstract

In this work we investigate the weak lensing convergence using an end-to-end nonlinear general relativistic framework. Combining numerical relativity simulations of large-scale structure formation with general relativistic ray-tracing, we compare our nonlinear calculation to the expectation based on perturbation theory for a set of 20 synthetic observers. We focus on large angular scales $\ell < 100$ across a broad range of redshifts with $0.05<z<3$. We confirm the importance of Doppler lensing for redshifts below $z\sim$0.6, as predicted by previous works. On average across our observers, linear perturbation theory predicts the nonlinear convergence to within 3-30% across all redshifts and angular scales we study. In general, we find smaller angular scales are better matched by linear theory than larger angular scales. While we cannot definitively identify the source of the discrepancy, for our particular study of redshift slices on observers' light cones the differences are mostly below the level of cosmic variance.