The Stringy Origins of Galileons and their Novel Limit

TL;DR

This paper demonstrates that generalized Galileons, a subclass of Horndeski gravity, originate from heterotic string theory via Kaluza-Klein reduction, revealing a string-theoretic basis for certain scalar-tensor theories of gravity.

Contribution

It shows that specific Horndeski theories, including Galileons, can be derived from string theory, and identifies a new limit through rescaling of the string parameter.

Findings

Galileons arise from heterotic string theory via Kaluza-Klein reduction

The form of Galileonic terms is fixed by the embedding spacetime parameters

A novel limit is introduced by rescaling the string parameter '

Abstract

We show generalized Galileons -- a particular subclass of Horndeski gravity -- arise from a consistent Kaluza-Klein reduction of the low-energy effective action of heterotic string theory to first order in $\alpha'$. This suggests Horndeski theories of gravity have a string-theoretic origin. The form of the Galileonic terms is precisely fixed by parameters of the embedding spacetime, so that only a specific subset of Horndeski theories is permitted by string theory. A novel limit of the model is considered by performing a dimensionful rescaling of $\alpha'$.