Extending the Gravitational Growth Framework

TL;DR

This paper extends the gravitational growth index formalism by adding an early time parameter g_star, enabling better testing of deviations from general relativity and dark energy models at high redshift.

Contribution

The authors introduce an extended formalism with an additional early time parameter g_star for improved modeling of large scale structure growth.

Findings

g_star effectively captures early universe modifications

Future data can constrain dark energy and gravity parameters simultaneously

Extended formalism improves tests of modified gravity models

Abstract

The gravitational growth index formalism provides a model independent way to look for deviations from general relativity by testing dark energy physics distinct from its effects on the cosmic expansion history. Here we extend the approach to incorporate an early time parameter g_star in addition to the growth index in describing the growth of large scale structure. We illustrate its utility for models with modified gravity at high redshift, early acceleration, or early dark energy. Future data will have the capability to constrain the dark energy equation of state, the growth index gamma, and g_star simultaneously, with no degradation in the equation of state determination.