Multi-Galileons in Curved Space

TL;DR

This paper constructs multi-field galileon and DBI theories in curved de Sitter space using probe brane methods, revealing novel symmetry-breaking vacua and strongly coupled Goldstone modes with implications for ghost-free models.

Contribution

It extends galileon and DBI theories to curved spaces with multiple fields and internal symmetries, exploring their vacuum structure and stability.

Findings

Existence of multiple de Sitter vacua with different ghost properties

Identification of strongly coupled Goldstone modes in certain vacua

Construction of theories with non-linear symmetries in curved space

Abstract

Using the probe brane construction of higher derivative effective field theories, extended to higher co-dimensions and curved spaces, we construct galileon and DBI theories on de Sitter space with N fields and an so(N) internal symmetry, non-linearly realizing the symmetries of a higher dimensional de Sitter space. In some cases, the theory admits a non-trivial vacuum that spontaneously breaks the so(N) symmetry, and around this vacuum the Goldstone modes have vanishing kinetic terms and become infinitely strongly coupled. This gives an example of a scalar effective field theory with two de Sitter vacua, one of which appears to have Boulware-Deser-like ghosts, and one of which does not.