Galileon gravity and its relevance to late time cosmic acceleration

TL;DR

This paper investigates covariant galileon gravity, analyzing its stability, suppression of fifth forces, and effects on cosmic acceleration, including extensions to higher-order theories and implications for matter perturbations.

Contribution

It extends galileon gravity analysis to fifth order theories, demonstrating stability and conditions for fifth force suppression in spherically symmetric backgrounds.

Findings

Stable self-accelerating solutions identified.

Conditions for fifth force suppression derived.

Evolution equations for matter perturbations obtained.

Abstract

We consider the covariant galileon gravity taking into account the third order and fourth order scalar field Lagrangians L_3(\pi) and L_4(\pi) consisting of three and four $\pi$'s with four and five derivatives acting on them respectively. The background dynamical equations are set up for the system under consideration and the stability of the self accelerating solution is demonstrated in general setting. We extended this study to the general case of the fifth order theory. For spherically symmetric static background, we spell out conditions for suppression of fifth force effects mediated by the galileon field $\pi$. We study the field perturbations in the fixed background and investigate conditions for their causal propagation. We also briefly discuss metric fluctuations and derive evolution equation for matter perturbations in galileon gravity.