New terms for scalar multi-Galileon models and application to SO(N) and SU(N) group representations

TL;DR

This paper introduces a new class of scalar multi-galileon models, explores their symmetry properties, and applies them to SO(N) and SU(N) group representations, expanding the understanding of multi-galileon dynamics.

Contribution

It defines a novel class of multi-galileon Lagrangians not covered by existing formulations and analyzes their symmetry properties and dynamics within specific group representations.

Findings

New multi-galileon Lagrangians identified and characterized.

Symmetry properties elucidated, revealing hidden symmetries.

Consistent dynamics confirmed through symmetry-based analysis.

Abstract

We investigate a new class of scalar multi-galileon models, which is not included in the commonly admitted general formulation of generalized multi-galileons. The Lagrangians of this class of models, some of them having already been introduced in previous works, are specific to multi-galileon theories, and vanish in the single galileon case. We examine them in details, discussing in particular some hidden symmetry properties which can be made explicit by adding total derivatives to these Lagrangians. These properties allow us to describe the possible dynamics for these new Lagrangians in the case of multi-galileons in the fundamental representation of a SO(N) and SU(N) global symmetry group, as well as in the adjoint representation of a SU(N) global symmetry group. We perform in parallel an exhaustive examination of some of these models, finding a complete agreement with the dynamics obtained using the symmetry properties. Finally, we conclude by discussing what could be the most general multi-galileon theory, as well as the link between scalar and vector multi-galileon models.