by Dr. Biswajit Sahoo, King's College, London

Abstract :

Scattering amplitudes play a central role in understanding fundamental interactions, offering a unifying framework for both quantum field theory and quantum gravity. In this seminar, I will present my research on perturbative and non-perturbative aspects of scattering amplitudes, focusing on two main directions. On the perturbative side, I will show how soft graviton theorems, which capture universal features of the gravitational S-matrix, determine the low-frequency behavior of gravitational radiation in the classical limit. I will outline how these results enable the derivation of waveforms for general classical scattering processes and explore their implications for gravitational tail memory effects, as well as their potential observational signatures in current gravitational-wave experiments. On the non-perturbative side, I will describe how S-matrix, form factor, and spectral density bootstrap techniques can be used to constrain renormalization group flows, providing new tools to study strongly coupled quantum field theories through principles such as unitarity and analyticity. This framework offers insights into the structure of renormalization group flows in both Lorentz-invariant and Lorentz-violating systems, particularly those connecting conformal field theories in the ultraviolet to gapped phases in the infrared.