High Energy Physics Seminar
The double-copy is a remarkable multiplicative structure on the landscape of quantum field theories, best known by the canonical example: "gravity = (Yang-Mills)^2". Over several decades of exploration, numerous additional, non-gauge theory, examples of "colorful" models with a consistent double-copy have been identified. Despite this progress, the rules-of-the-game are not completely understood, and the full extent of the landscape of double-copy compatible models remains largely unknown. In this talk I will describe recent attempts to generalize the double-copy to models incorporating massive states and higher-derivative interactions. One of the key results is the observation that color-kinematics duality is not a sufficient condition for the double-copy to produce a physical scattering amplitude. We find that in addition, imposing a "minimal rank" condition on the zeroth copy scattering amplitudes removes all non-physical singularities. I will present two primary applications of this result. The first is to models with massive states, in this context the rank condition translates into a set of linear constraints on the mass spectrum, and as a consequence I will demonstrate a no-go result for attempts to realize massive gravity as a double-copy. The second application is to incorporating higher-derivative corrections to massless models. I will show how the most general, minimal rank, zeroth copy can be efficiently "bootstrapped" order-by-order in a derivative expansion. The result is a vast generalization of the string theory KLT formula that allows for the double-copy of the most general set of higher-derivative corrections to Yang-Mills, encompassing and extending previous attempts.