Color-Kinematics Duality in Multi-Regge Kinematics and Dimensional Reduction
Henrik Johansson, Agustin Sabio Vera, Eduardo Serna Campillo, Miguel A. Vazquez-Mozo
TL;DR
This paper addresses whether color-kinematics duality can reproduce gravity amplitudes for tree-level scattering of scalar matter with emission in multi-Regge kinematics. By considering two extensions—a scalar quartic contact interaction arising from dimensional reduction of higher-dimensional YM theories and indistinguishable adjoint scalars—the authors show that the BCJ double-copy yields the full gravitational amplitude in MRK, including the necessary -N^μN^ν piece. The results connect the success of the double-copy to higher-dimensional embeddings (N=2 bosonic sector and dimensional reductions from D=6 or D=5 YM) and clarify how matter content can be accommodated within CK duality. These findings suggest a path toward generalizing the double-copy to more complex matter sectors, while highlighting open questions about matter states beyond the studied cases.
Abstract
In this note we study the applicability of the color-kinematics duality to the scattering of two distinguishable scalar matter particles with gluon emission in QCD, or graviton emission in Einstein gravity. Previous analysis suggested that direct use of the Bern-Carrasco-Johansson double-copy prescription to matter amplitudes does not reproduce the gravitational amplitude in multi-Regge kinematics. This situation, however, can be avoided by extensions to the gauge theory, while maintaning the same Regge limit. Here we present two examples of these extensions: the introduction of a scalar contact interaction and the relaxation of the distinguishability of the scalars. In both cases new diagrams allow for a full reconstruction of the correct Regge limit on the gravitational side. Both modifications correspond to theories obtained by dimensional reduction from higher-dimensional gauge theories.