How to Falsify the GR+LambdaCDM Model with Galaxy Redshift Surveys

TL;DR

This paper proposes two model-independent tests, epsilon and upsilon, to detect deviations from the GR+LambdaCDM cosmological model using galaxy redshift surveys, offering a new way to test fundamental physics.

Contribution

It introduces the upsilon test for scale-dependence in structure growth and assesses the constraining power of upcoming surveys on these tests.

Findings

Upcoming surveys can constrain epsilon and upsilon at 5-10% levels.

Higher redshift, lower bias galaxies are more effective for detecting deviations.

The tests provide stringent, model-independent checks of the standard cosmological model.

Abstract

A wide range of models describing modifications to General Relativity have been proposed, but no fundamental parameter set exists to describe them. Similarly, no fundamental theory exists for dark energy to parameterize its potential deviation from a cosmological constant. This motivates a model-independent search for deviations from the concordance GR+LambdaCDM cosmological model in large galaxy redshift surveys. We describe two model-independent tests of the growth of cosmological structure, in the form of quantities that must equal one if GR+LambdaCDM is correct. The first, epsilon, was introduced previously as a scale-independent consistency check between the expansion history and structure growth. The second, upsilon, is introduced here as a test of scale-dependence in the linear evolution of matter density perturbations. We show that the ongoing and near-future galaxy redshift surveys WiggleZ, BOSS, and HETDEX will constrain these quantities at the 5-10% level, representing a stringent test of concordance cosmology at different redshifts. When redshift space distortions are used to probe the growth of cosmological structure, galaxies at higher redshift with lower bias are found to be most powerful in detecting deviations from the GR+LambdaCDM model.