Galileons on Trial

TL;DR

Galileon gravity, an alternative to general relativity for cosmic acceleration, faces significant observational constraints that challenge its viability, especially models without direct matter coupling.

Contribution

This paper demonstrates that Galileon models cannot simultaneously match cosmic expansion and growth histories, and current data strongly disfavor non-matter-coupled variants.

Findings

Current observations disfavor many Galileon models

Galileon models cannot fit both expansion and growth histories simultaneously

Models without direct matter coupling are ruled out as alternatives to DM

Abstract

Galileon gravity is a robust theoretical alternative to general relativity with a cosmological constant for explaining cosmic acceleration, with interesting properties such as having second order field equations and a shift symmetry. While either its predictions for the cosmic expansion or growth histories can approach standard \Lambda CDM, we demonstrate the incompatibility of both doing so simultaneously. Already current observational constraints can severely disfavor an entire class of Galileon gravity models that do not couple directly to matter, ruling them out as an alternative to \Lambda CDM.