Classical and Semiclassical Aspects of Amplitudes

Recently, an entirely new class of observable in quantum field theory has been discovered. These observables, which I discovered with my collaborators, make contact with the exciting physics of gravitational waves, and have been used to determine the state-of-the-art expression for the gravitational waveform emitted as two black holes scatter. Yet these observables, given in terms of scattering amplitudes, also lead to a number of major open questions:1. How can we compute bound state gravitational waveforms from quantum field theory?2. What is the infrared physics of the new observables?3. The observables are quantum-mechanical at their heart. Can we use them to compute the Hawking radiation, for the first time, in full quantum field theory?Answers to these questions will transform our understanding of the quantum field theory of gravity.