2023/08/22 by Du, Yuchen, Vaman, Diana · 1 citation
#FOS: Physical sciences #High Energy Physics - Theory (hep-th)
paper · doi:10.48550/arxiv.2308.11326
We use the worldline formalism to study tree-level scattering processes involving gravitons. A massless spin 2 particle is described by an N=4 supersymmetric worldline action which is also O(4) symmetric. More generally, N=2S supersymmetric worldline actions exhibiting O(N) symmetry describe free spin S particles. Recently a BRST approach was used to construct the on-shell background graviton emission vertex from a graviton worldline. Nonetheless, an action describing the coupling of higher spin (S≥ 2) particles with generic background gravity is unknown. In this paper, we found that in order to reproduce Einstein's general relativity 3-point graviton vertex, interpreted as the emission of an off-shell graviton from the worldline, the coupling to background gravity must break the O(4) symmetry to O(2) × O(2). In addition to this symmetry-breaking feature, we also found that the coefficient β of the worldline action counterterm βR differs from previous results in the literature. By comparing the linearized graviton and photon emission vertex operators from different worldlines, we noticed that they obey a squaring relation. For MHV (Maximal Helicity Violating) amplitudes, these squaring relations among the linearized vertex operators directly result in double-copy-like relations between the scattering amplitudes.