Spinning waveforms of scalar radiation in quadratic modified gravity

TL;DR

This paper employs on-shell amplitude methods to compute scalar radiation waveforms in quadratic modified gravity theories, incorporating spin effects and analyzing the impact of contact terms on the amplitude.

Contribution

It introduces a novel application of amplitude techniques to scalar-tensor theories with Gauss-Bonnet and Chern-Simons terms, including detailed waveform calculations and contact term analysis.

Findings

Waveforms for scalar radiation in modified gravity are explicitly calculated.

The dependence of amplitudes on contact terms is clarified.

Conditions for detecting classical scalar radiation are discussed.

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.