Redshift Distortions as a Probe of Gravity

TL;DR

This paper discusses how redshift distortions in galaxy surveys can be used to test gravity theories, offering a method less affected by uncertainties in cosmic expansion, and addresses biases in traditional matter density estimates.

Contribution

It introduces a gravity-sensitive approach using redshift distortions that minimizes dependence on the cosmic expansion's equation of state.

Findings

Redshift distortions can effectively distinguish gravity theories.

Traditional methods like f=Omega_m^{0.6} can be biased.

Proposed methods reduce bias in matter density measurements.

Abstract

Redshift distortion measurements from galaxy surveys include sensitivity to the gravitational growth index distinguishing other theories from Einstein gravity. This gravitational sensitivity is substantially free from uncertainty in the effective equation of state of the cosmic expansion history. We also illustrate the bias in the traditional application to matter density determination using f=Omega_m(a)^{0.6}, and how to avoid it.