Spinning waveforms of scalar radiation in quadratic modified gravity

Abstract

We study scalar-tensor gravitational theories using on-shell amplitude methods. We focus on theories with gravity coupled to a massless scalar via the Gauss-Bonnet and Chern-Simons terms. In this framework, we calculate the waveforms for classical scalar radiation emitted in scattering of macroscopic objects, including spin effects. To this end, we use the Kosower-Maybee-O'Connell formalism, with the 5-particle amplitude for scalar emission in matter scattering calculated at tree level using the unitarity-factorization bootstrap techniques. We also discuss in detail the dependence of that amplitude on the contact terms of the intermediate 4-particle scalar-graviton-matter amplitude. Finally, we discuss the conditions for resolvability of classical scalar radiation.