vbid/9783319201283

Description

Starting from the earlier notions of stationary action principles, these tutorial notes shows how Schwinger�s Quantum Action Principle descended from Dirac�s formulation, which independently led Feynman to his path-integral formulation of quantum mechanics. Part I brings out in more detail the connection between the two formulations, and applications are discussed. Then, the Keldysh-Schwinger time-cycle method of extracting matrix elements is described. Part II will discuss the variational formulation of quantum electrodynamics and the development of source theory.Typham this is the title: Schwinger’s Quantum Action Principle From Dirac�s Formulation Through Feynman�s Path Integrals, the Schwinger-Keldysh Method, Quantum Field Theory, to Source Theory