Double Copy for Massive Scalar Field Theories

TL;DR

This paper extends the double copy framework to massive scalar theories, demonstrating a relation between certain massive theories via dimensional reduction and identifying new cubic interactions consistent with BCJ relations.

Contribution

It introduces a new cubic theory with a local double copy and explores the double copy structure of massive scalar theories through dimensional reduction.

Findings

A double copy relation exists between massive 4D scalar theories derived from 5D models.

A new cubic interaction satisfying BCJ relations up to 5-point amplitudes is identified.

The vanishing of certain high-dimensional galileon terms is crucial for the double copy construction.

Abstract

We explore extensions of the double copy to massive theories and find a new cubic theory with a local double copy. We consider the nonlinear sigma model and the special galileon theory, massless versions of which are known to be related through the double copy. We show that by performing a Kaluza-Klein reduction of these theories from five dimensions down to four, a double copy relation exists between the resulting massive four-dimensional scalar field theories. This requires the vanishing contribution of new galileon terms arising in high dimensions. We further explore if other interactions that do not arise from a dimensional reduction of the nonlinear sigma model could be double copied and find a new cubic interaction which satisfies the BCJ relations up to 5-point amplitudes.