Weak lensing by voids in modified lensing potentials

TL;DR

This paper investigates how voids in the universe affect gravitational lensing in modified gravity theories, showing that void lensing signals can significantly differ from general relativity, offering a way to test such theories.

Contribution

It provides analytical and simulation-based analysis of void lensing signals in Cubic Galileon and Nonlocal gravity models, highlighting their potential for testing modified gravity.

Findings

Cubic Galileon voids nearly double lensing effects compared to GR.

Modified density profiles and fifth forces slightly increase lensing in Nonlocal models.

Void lensing signals are promising probes for testing gravity modifications.

Abstract

We study lensing by voids in Cubic Galileon and Nonlocal gravity cosmologies, which are examples of theories of gravity that modify the lensing potential. We find voids in the dark matter and halo density fields of N-body simulations and compute their lensing signal analytically from the void density profiles, which we show are well fit by a simple analytical formula. In the Cubic Galileon model, the modifications to gravity inside voids are not screened and they approximately double the size of the lensing effects compared to GR. The difference is largely determined by the direct effects of the fifth force on lensing and less so by the modified density profiles. For this model, we also discuss the subtle impact on the force and lensing calculations caused by the screening effects of haloes that exist in and around voids. In the Nonlocal model, the impact of the modified density profiles and the direct modifications to lensing are comparable, but they boost the lensing signal by only $\approx 10\%$, compared with that of GR. Overall, our results suggest that lensing by voids is a promising tool to test models of gravity that modify lensing.