Amplitudes for Classical and Quantum Gravity

AmpGravity will employ amplitudes techniques to progress the fronts of classical (Objective 1) and quantum (Objective 2) gravity, while exploring the rich interplay of the two. Objective 1: Calculations based on scattering amplitudes in Quantum Field Theory (QFT) have significantly increased the accuracy of models for the evolution of astrophysical binaries in General Relativity. Kosmopoulos' results in particular have been imported into recent versions of the Effective-One-Body formalism, the main model used for gravitational-wave-template production by the LIGO, Virgo, and KAGRA collaboration. Kosmopoulos will push the state-of-the-art to meet the precision goals of the next-generation observatories by performing the necessary calculations for binaries of spinning objects and developing non-perturbative methods pertinent in the strong-coupling regime. Objective 2: Low-energy gravitational theories must obey consistency conditions, such as unitarity and causality, to be embedded in a complete theory of quantum gravity valid at all energy scales. Amplitudes in conjunction with dispersion relations are a natural language to derive such consistency conditions. Kosmopoulos will use these quantum-gravity considerations to obtain bounds on quantities of interest for the classical problem of gravitational-wave physics, such as the stress tensor and tidal-response coefficients for black holes and neutron stars. In turn, he will improve these methods by including known universal behavior of gravitational amplitudes, namely the eikonal limit established in a regime controlled by classical physics, and use them to derive properties of quantum gravity.