Massive gravity coupled to DBI Galileons is ghost free

TL;DR

This paper demonstrates a ghost-free coupling of Dirac-Born-Infeld scalars with Galilean symmetry to nonlinear massive gravity, preserving the desirable features of both theories and avoiding the Boulware-Deser ghost.

Contribution

It introduces a novel coupling of DBI Galileons to massive gravity that maintains Galilean symmetry and ensures the theory is ghost-free.

Findings

The coupled theory has the primary constraint to eliminate the Boulware-Deser ghost.

The construction preserves the properties of Galileons and massive gravity.

The approach extends the class of consistent scalar-tensor theories with symmetry.

Abstract

It is possible to couple Dirac-Born-Infeld (DBI) scalars possessing generalized Galilean internal shift symmetries (Galileons) to nonlinear massive gravity in four dimensions, in such a manner that the interactions maintain the Galilean symmetry. Such a construction is of interest because it is not possible to couple such fields to massless General Relativity in the same way. We show that this theory has the primary constraint necessary to eliminate the Boulware-Deser ghost, thus preserving the attractive properties of both the Galileons and ghost-free massive gravity.