Detectability of Weak Lensing Modifications under Galileon Theories

TL;DR

This paper investigates the potential to detect small modifications in gravitational lensing caused by Galileon theories using future large-scale surveys, aiming to test these theories against standard cosmology.

Contribution

It demonstrates that upcoming photometric surveys like LSST could detect or strongly exclude Galileon modifications at a 4-sigma level using halo-shear power spectra analysis.

Findings

Galileon modifications can be detected at up to 4-sigma significance.

Non-detection can strongly exclude the Galileon model.

Next-generation surveys have the potential to test modified gravity theories.

Abstract

Theories of modified gravity attempt to reconcile physics at the largest and the smallest scales by explaining the accelerated expansion of our universe without introducing the cosmological constant. One class of such theories, known as Galileon theories, predict lensing potentials of spherically symmetric bodies, such as dark matter halos, to receive a feature-like modification at the 5% level. With the advent of next-generation photometric surveys, such modifications can serve as novel probes of modified gravity. Assuming an LSST-like fiducial dataset, we produce halo-shear power spectra for LCDM and Galileon scenarios, and perform a Fisher analysis including cosmological, nuisance, and Galileon parameters to study the detectability of the aforementioned modifications. With the LCDM scenario as our null hypothesis, we conclude that it is possible to detect the Galileon modifications at up to 4-{\sigma} if present, or strongly exclude the model in a non-detection, with a tomography of four redshift bins and four mass bins, an LSST-like set of survey parameters, and Planck priors on cosmological parameters.