Galileons with Gauge Symmetries

TL;DR

This paper extends galileon models to include local gauge symmetries and curved spacetime, ensuring second order equations of motion and avoiding ghosts, thus broadening their theoretical framework and potential applications.

Contribution

It introduces a natural generalization of galileon theories to gauge fields and curved space, maintaining second order derivatives and avoiding Ostrogradski ghosts.

Findings

Galileon models can be coupled to Yang-Mills fields with second order equations.

Non-minimal couplings are necessary in curved space to preserve second order nature.

The extended models avoid Ostrogradski ghosts in gauge and curved backgrounds.

Abstract

Galileon models arise in certain braneworld scenarios as modifications to General Relativity, and are also interesting as field theories in their own right. We show how the galileon model can be naturally generalized to include local gauge symmetries, by allowing for couplings to Yang-Mills fields. The resulting theories have at most second order spacetime derivatives in any representation of the gauge group, thereby avoiding Ostrogradski ghosts. We also extend the models to include curved space, and show how in that case we need to include non-minimal couplings between the galileons and the curvature tensors for the theory to retain its second order nature.