Model-independent constraints on modified gravity from current data and from the Euclid and SKA future surveys

TL;DR

This paper investigates constraints on modified gravity using current and future cosmological data, accounting for additional free parameters to achieve a more model-independent analysis, and explores potential exclusion regions for specific gravity models.

Contribution

It introduces a more flexible, model-independent approach to constrain modified gravity parameters using current and forecasted data, including scale-dependent effects.

Findings

Constraints weaken when additional free parameters are included.

Current data provide limited bounds on the Poisson parameter Y.

Future surveys like Euclid and SKA can improve constraints and exclude certain gravity models.

Abstract

The aim of this paper is to constrain modified gravity with redshift space distortion observations and supernovae measurements. Compared with a standard LCDM analysis, we include three additional free parameters, namely the initial conditions of the matter perturbations,the overall perturbation normalization, and a scale-dependent Y parameter modifying the Poisson equation, in an attempt to perform a more model-independent analysis. First, we constrain the Poisson parameter Y (also called Geff ) by using currently available fsigma_8 data and the recent SN catalog JLA. We find that the inclusion of the additional free parameters makes the constraints significantly weaker than when fixing them to the standard cosmological value. Second, we constrain Y by using forecast growth-rate data for Euclid and SKA missions. Here again we point out the weakening of the constraints when the additional parameters are included. Finally, we adopt as modified gravity Poisson parameter the specific Horndeski form, and use scale-dependent forecasts to build an exclusion plot for the Yukawa potential akin to the ones realized in laboratory experiments, both for the Euclid and the SKA surveys.