Model-independent cosmological constraints from growth and expansion

TL;DR

This paper reconstructs the universe's expansion history using supernova data and growth rate measurements to place model-independent constraints on key cosmological parameters, supporting the standard model but not ruling out modifications.

Contribution

It provides a model-independent method to constrain cosmological parameters from growth and expansion data, reinforcing the concordance model with minimal assumptions.

Findings

Constraints align with the standard cosmological model within general relativity.

Current data quality is insufficient to exclude modified gravity.

Positivity condition on dark energy density further supports the concordance model.

Abstract

Reconstructing the expansion history of the Universe from type Ia supernovae data, we fit the growth rate measurements and put model-independent constraints on some key cosmological parameters, namely, $\Omega_\mathrm{m},\gamma$, and $\sigma_8$. The constraints are consistent with those from the concordance model within the framework of general relativity, but the current quality of the data is not sufficient to rule out modified gravity models. Adding the condition that dark energy density should be positive at all redshifts, independently of its equation of state, further constrains the parameters and interestingly supports the concordance model.