A novel null test for the $\Lambda$CDM model with growth-rate data

TL;DR

This paper introduces a new, model-independent null test based on growth-rate data to evaluate the consistency of the $\\Lambda$CDM model and explore potential deviations such as clustering dark energy or modified gravity.

Contribution

It proposes an alternative, model-independent consistency check at the perturbative level using growth of matter perturbations data.

Findings

Provides a new null test for the $\\Lambda$CDM model.

Can distinguish between clustering dark energy and modified gravity.

Applicable to current and future high-precision surveys.

Abstract

Current and upcoming surveys will measure the cosmological parameters with an extremely high accuracy. The primary goal of these observations is to eliminate some of the currently viable cosmological models created to explain the late time accelerated expansion (either real or only inferred). However, most of the statistical tests used in cosmology have a strong requirement: the use of a model to fit the data. Recently there has been an increased interest on finding tests that are model independent, i.e. to have a function that depends entirely on observed quantities and not on the model, see for instance [1]. In this letter we present an alternative consistency check at the perturbative level for a homogeneous and isotropic Universe filled with a dark energy component. This test makes use of the growth of matter perturbations data and it is able to not only test the homogeneous and isotropic Universe but also, within the framework of a Friedmann-Lema\^itre-Robertson-Walker Universe, if the dark energy component is able to cluster, if there is a tension in the data or if we are dealing with a modification of gravity.