HEP Theory Journal Club

Nonperturbative uses of Feynman diagrams: from the Hydrogen atom to Black holes

Miguel Correia

McGill University

The amplitude for scattering of relativistic particles can be computed perturbatively via the use of Feynman diagrams. However, in many physical systems there is no obvious small coupling for which the standard Feynman expansion applies. These include the mundane Hydrogen atom, in which the electron becomes bound to the proton, or the scattering of astrophysical objects whose mass is much larger than the Planck mass. In this talk I am going to describe how, in certain regimes, the Feynman diagram expansion can be re-organized and re-summed in order to apply to such systems. I will show how quantities such as the Hydrogen spectrum, the positronium decay rate, or Mercury's perihelion precession can be derived from Feynman diagrams. I will then overview the use of Feynman diagrams for gravitational wave physics and black hole binary inspirals, and what are the current open challenges.