The decoupling limit of Multi-Gravity: Multi-Galileons, Dualities and More

TL;DR

This paper explores the decoupling limit of multi-gravity theories, revealing multi-Galileon interactions and dualities, and extends Galileon dualities to new multi-scalar field theories related to beyond Horndeski models.

Contribution

It explicitly computes helicity-0 interactions in multi-gravity, introduces new multi-Galileon dualities, and connects them to higher-derivative scalar theories.

Findings

Derived multi-Galileon dualities.

Extended Galileon dualities to multi-scalar theories.

Connected dualities to beyond Horndeski models.

Abstract

In this paper we investigate the decoupling limit of a particular class of multi-gravity theories, i.e. of theories of interacting spin-2 fields. We explicitly compute the interactions of helicity-0 modes in this limit, showing that they take on the form of multi-Galileons and dual forms. In the process we extend the recently discovered Galileon dualities, deriving a set of new multi-Galileon dualities. These are also intrinsically connected to healthy, but higher-derivative, multi-scalar field theories akin to `beyond Horndeski' models.