Constraining Galileon gravity from observational data with growth rate

TL;DR

This paper evaluates the constraints on Galileon gravity using various observational data, finding it less compatible with observations than the standard Lambda Cold Dark Matter model, mainly due to differences in growth rate predictions.

Contribution

It provides the first comprehensive observational constraints on Galileon gravity using growth rate, SN Ia, CMB, and BAO data, highlighting its incompatibility with current observations.

Findings

Galileon models predict higher growth rates than LambdaCDM.

Best-fit matter density parameter in Galileon models is smaller than observationally supported.

Galileon models are less compatible with combined observational data than LambdaCDM.

Abstract

We studied the cosmological constraints on the Galileon gravity obtained from observational data of the growth rate of matter density perturbations, the supernovae Ia (SN Ia), the cosmic microwave background (CMB), and baryon acoustic oscillations (BAO). For the same value of the energy density parameter of matter $\Omega_{m,0}$, the growth rate $f$ in Galileon models is enhanced, relative to the $\Lambda$CDM case, because of an increase in Newton's constant. The smaller $\Omega_{m,0}$ is, the more growth rate is suppressed. Therefore, the best fit value of $\Omega_{m,0}$ in the Galileon model, based only the growth rate data, is quite small. This is incompatible with the value of $\Omega_{m,0}$ obtained from the combination of SN Ia, CMB, and BAO data. On the other hand, in the $\Lambda$CDM model, the values of $\Omega_{m,0}$ obtained from different observational data sets are consistent. In the analysis of this paper, we found that the Galileon model is less compatible with observations than the $\Lambda$CDM model. This result seems to be qualitatively the same in most of the generalized Galileon models in which Newton's constant is enhanced.