Classical physics from amplitudes on curved backgrounds

Abstract

We generalise the Kosower-Maybee-O'Connell (KMOC) formalism relating classical observables and scattering amplitudes to curved backgrounds. We show how to compute the final semiclassical state for a particle moving in a curved background in terms of scattering amplitudes on that background. Two-point amplitudes in this framework correspond to conservative physics with background-dependent memory effects. As an application, we consider plane wave and shockwave backgrounds both in electromagnetism and general relativity. We determine the final semiclassical state, showing it satisfies a notion of double copy on curved backgrounds. We then conclude by computing the impulse of a particle on such backgrounds, deriving exact results and velocity memory effects.

15 pages

References in corpus (7)

• Infrared Divergences in QED, Revisited
• Scattering on plane waves and the double copy
• Shaving off Black Hole Soft Hair
• Large Gauge Symmetries and Asymptotic States in QED
• Classical observables from coherent-spin amplitudes
• Graviton particle statistics and coherent states from classical scattering amplitudes
• Memory, Penrose Limits and the Geometry of Gravitational Shockwaves and Gyratons