Covariant multi-galileons and their generalisation

TL;DR

This paper develops a covariant extension of multi-galileon theories that maintains second-order equations and generalizes to include multiple scalars and a tensor, potentially broadening scalar-tensor gravity models.

Contribution

It introduces a covariant multi-galileon framework and extends it to a larger class of second-order scalar-tensor theories, possibly generalizing Horndeski's theory.

Findings

Covariant multi-galileon theories with second-order equations derived.

Generalization to multiple scalars and a tensor achieved.

Conjecture that these form a multi-scalar extension of Horndeski's theory.

Abstract

We find a covariant completion of the flat-space multi-galileon theory, preserving second-order field equations. We then generalise this to arrive at an enlarged class of second order theories describing multiple scalars and a single tensor, and conjecture that these are a multi-scalar version of Horndeski's most general scalar-tensor theory.