The Radiative Double Copy for Einstein-Yang-Mills Theory
David Chester
TL;DR
The paper establishes a leading-order radiative double copy between Yang-Mills–biadjoint-scalar theory and Einstein–Yang–Mills theory within a weak-field expansion, identifying the trace-reversed metric $\bar{h}^{\mu\nu}$ as the double copy of the gauge field $A^{\mu a}$. It develops a perturbative framework for classical radiation, computes the YM–biadjoint-scalar radiative currents and fields, and then derives the corresponding gravitational radiation in EYM theory. By applying explicit replacement rules, it demonstrates that the gravitational radiation source $\hat{T}^{\mu\nu}$ is reproduced from gauge theory data at leading order, confirming the radiative double-copy relation and its gauge-invariant organization via pseudotensors and three-point vertices. The work also shows how Einstein–Maxwell theory emerges as a special case and outlines prospects for extending the double copy to higher orders, potentially aiding complex gravitational-radiation calculations relevant to observations such as LIGO.
Abstract
Recently, a double-copy formalism was used to calculate gravitational radiation from classical Yang-Mills radiation solutions. This work shows that Yang-Mills theory coupled to a biadjoint scalar field admits a radiative double copy that agrees with solutions in Einstein-Yang-Mills theory at the lowest finite order. Within this context, the trace-reversed metric $\bar{h}^{μν}$ is a natural double copy of the gauge boson $A^{μa}$. This work provides additional evidence that solutions in gauge and gravity theories are related, even though their respective Lagrangians and nonlinear equations of motion appear to be different.
