The SAGEX Review on Scattering Amplitudes, Chapter 2: An Invitation to Color-Kinematics Duality and the Double Copy

TL;DR

This review discusses recent progress in scattering amplitudes, focusing on color-kinematics duality and the double copy, which simplify calculations and suggest a unified framework for quantum theories, with applications to gravity and gravitational waves.

Contribution

It provides an accessible overview of color-kinematics duality and the double copy, including examples and applications in gravitational-wave physics, highlighting their role in simplifying complex calculations.

Findings

Identification of double-copy-constructible theories

Application of double copy to gravitational-wave calculations

Simplification of higher-order scattering amplitude computations

Abstract

Advances in scattering amplitudes have exposed previously-hidden color-kinematics and double-copy structures in theories ranging from gauge and gravity theories to effective field theories such as chiral perturbation theory and the Born-Infeld model. These novel structures both simplify higher-order calculations and pose tantalizing questions related to a unified framework underlying relativistic quantum theories. This introductory mini-review article invites further exploration of these topics. After a brief introduction to color-kinematics duality and the double copy as they emerges at tree and loop-level in gauge and gravity theories, we present two distinct examples: 1) an introduction to the web of double-copy-constructible theories, and 2) a discussion on the application of the double copy to calculation relevant to gravitational-wave physics.