Gravitational scattering and classical observables

• Grant number: 25/01291-6
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: October 01, 2025
• End date: September 30, 2027
• Field of knowledge: Physical Sciences and Mathematics - Physics - General Physics
• Principal Investigator: Riccardo Sturani
• Grantee: Samim Akhtar
• Host Institution: Instituto de Física Teórica (IFT). Universidade Estadual Paulista (UNESP). Campus de São Paulo. São Paulo , SP, Brazil
• Associated research grant: 22/06350-2 - Fundamental physics and LIGO, AP.ESP

Abstract

This project lies at the interface between theoretical high-energy physicsand classical gravity.Motivated by the current and future gravitational wave observations, which will demand waveform templates with higher and higher accuracy, the analyticstudy of two body dynamics, which is at the heart of the gravitationalwaveform prediction, has never been so vibrant.A popular approach is presently the KMOC, which computes scattering amplitudewith "on-shell" methods to compute classical observables which determine thegeneric 2-body gravitational dynamics.The KMOC formalism provides a significantly simpler way to compute theobservables as the classical limit is taken at thelevel of loop integrands, before evaluating the full amplitude. Additionally,the radiation reaction effects are naturally inbuilt within the framework.Moreover it allows a clear separation between classical and quantum observables,which makes it very suitable for comparison with NRGR, the method adoptedby the proposed post-doc supervisor that have been so successful in the pastto obtain results in the post-Newtonian approximation to General Relativity.In particular it is expected that the post-doc will help in the calculationof radiation-reaction-squared effects, which are three loop in the KMOC approachand representing at present the stumbling block preventing to completethe 5th perturbative order in post-Newtonian approximation to General Relativity.This project wishes to explore various radiation reaction effects (to impulse, energy and angular momentum) in the KMOC formalism to compare with the NRGR one,possibly extending the analysis to the spinning case.As a by-product, this project will investigate the classical limit ofsub-leading soft theorems, which describe the behavior of gravitational waveforms inthe low-frequency domain of the detector. This is the case of the well-knownmemory effect, which is simply the coefficient of the leading term in the soft expansion of the radiative field. (AU)