Hybrid Goldstone Modes from the Double Copy Bootstrap

TL;DR

This paper classifies scalar field theories with double copy amplitude formulations, revealing a new hybrid Goldstone mode with unique soft behavior and connections to known theories like DBI and Galileons.

Contribution

It identifies new building blocks for double copy scalar theories and introduces a novel theory involving Lovelock invariants with hybrid symmetry properties.

Findings

Classified scalar theories with double copy structure.

Discovered a new theory involving Lovelock invariants.

Revealed hybrid soft behavior regimes of Goldstone modes.

Abstract

We perform a systematic classification of scalar field theories whose amplitudes admit a double copy formulation and identify two building blocks at 4-point and 13 at 5-point. Using the 4-point blocks as bootstrap seeds, this naturally leads to a single copy theory that is a gauged NLSM. Moreover, its double copy includes a novel theory that can be written in terms of Lovelock invariants of an induced metric, and includes Dirac-Born-Infeld and the special Galileon in specific limits. The amplitudes of these Goldstone modes have two distinct soft behaviour regimes, corresponding to a hybrid of non-linear symmetries.