Bhatnagar, Shashank (PhD)Dinegde, Urga2018-07-092023-11-092018-07-092023-11-092007-03http://10.90.10.223:4000/handle/123456789/7211This thesis deals with the physics of two photon processes. We first introduce covariant perturbation theory and apply it to some quantum electrodynamics processes. We start with study of electron-positron pair production in the field of a static nucleus. We then deal with applications to electron-positron pair production through collision of virtual photons in high energy electron-electron scattering. Next we study the pair conversion of bremsstrahlung photon in high energy proton-proton scattering. Detailed evaluations of cross sections are givenenElectron-Positron pair ProductionThesis