KLT relations from the Einstein-Hilbert Lagrangian

TL;DR

This paper derives off-shell KLT relations from the Einstein-Hilbert Lagrangian, showing how gravity amplitudes relate to gauge theory amplitudes directly at the level of the action.

Contribution

It explicitly formulates KLT relations off-shell for three- and four-graviton vertices from the light-cone gravity Lagrangian.

Findings

KLT relations are made manifest off-shell for gravity

Relations are derived at the level of the action

Applicable to three- and four-graviton vertices

Abstract

The Kawai-Lewellen-Tye (KLT) relations derived from string theory tell us that perturbative gravity amplitudes are the "square" of the corresponding amplitudes in gauge theory. Starting from the light-cone Lagrangian for pure gravity we make these relations manifest off-shell, for three- and four-graviton vertices, at the level of the action.