Schwinger's Quantum Action Principle (Repost)
Kimball A. Milton, "Schwinger's Quantum Action Principle: From Dirac’s Formulation Through Feynman’s Path Integrals, the Schwinger-Keldysh Method, Quantum Field Theory, to Source Theory"
2015 | pages: 122 | ISBN: 3319201271 | PDF | 1,8 mb
2015 | pages: 122 | ISBN: 3319201271 | PDF | 1,8 mb
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.
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