Using cosmic voids to distinguish f(R) gravity in future galaxy surveys

TL;DR

This paper investigates how properties of cosmic voids in galaxy surveys can be used to distinguish f(R) gravity models from standard ext{LCDM} cosmology, forecasting the potential constraints future surveys could achieve.

Contribution

It introduces a method to use void properties from simulations to forecast the ability of upcoming surveys to test modified gravity models.

Findings

Stronger f(R) coupling eliminates small voids and enlarges some voids by ~20%.

Void emptiness and velocity profiles are significantly affected by modified gravity.

Future surveys could constrain the f(R) coupling strength to about 3×10⁻⁵.

Abstract

We use properties of void populations identified in $N$-body simulations to forecast the ability of upcoming galaxy surveys to differentiate models of f(R) gravity from \lcdm~cosmology. We analyze multiple simulation realizations, which were designed to mimic the expected number densities, volumes, and redshifts of the upcoming Euclid satellite and a lower-redshift ground-based counterpart survey, using the public {\tt VIDE} toolkit. We examine void abundances, ellipicities, radial density profiles, and radial velocity profiles at redshifts 1.0 and 0.43. We find that stronger f(R) coupling strengths eliminates small voids and produces voids up to $\sim 20\%$ larger in radius, leading to a significant tilt in the void number function. Additionally, under the influence of modified gravity, voids at all scales tend to be measurably emptier with correspondingly higher compensation walls. The velocity profiles reflect this, showing increased outflows inside voids and increased inflows outside voids. Using the void number function as an example, we forecast that future surveys can constrain the modified gravity coupling strength to $\sim 3 \times 10^{-5}$ using voids.