ACC0112http://www.osti.gov/accomplishments/documents/fullText/ACC0112.pdfThe Theory of Quantized Fields. IIISchwinger, J.May 1953NP-4565OSTI ID: 4368814Harvard University, Cambridge, Mass.6N-onr-24806US Atomic Energy Commission (AEC)Julian Schwinger and the Source Theory (http://www.osti.gov/accomplishments/schwinger.html)Field TheoryPhysics; Currents; Eigenfunctions; Eigenvalues; Electrodynamics; Electromagnetic Fields; Energy; Field Theory; Mathematics; Momentum; Photons; Quantum Electrodynamics; Quantum MechanicsIn this paper we discuss the electromagnetic field, as perturbed by a prescribed current. All quantities of physical interest in various situations, eigenvalues, eigenfunctions, and transformation probabilities, are derived from a general transformation function which is expressed in a non-Hermitian representation. The problems treated are: the determination of the energy-momentum eigenvalues and eigenfunctions for the isolated electromagnetic field, and the energy eigenvalues and eigenfunctions for the field perturbed by a time-independent current that departs from zero only within a finite time interval, and for a time-dependent current that assumes non-vanishing time-independent values initially and finally. The results are applied in a discussion of the intra-red catastrophe and of the adiabatic theorem. It is shown how the latter can be exploited to give a uniform formulation for all problems requiring the evaluation of transition probabilities or eigenvalue displacements.http://www.osti.gov/accomplishments/display_biblio.jsp?id=ACC0112&numPages=35&fp=N