THE BIRTH OF QUANTUM ELECTRODYNAMICS

FEYNMAN, RICHARD.

Space-time approach to quantum electrodynamics. (+)The Theory of Positrons.

Lancaster, American Physical Society, 1949.

Royal8vo. In contemporary full red cloth with gilt lettering to spine. In "The Physical Review", Second Series, Volume 76, Number 6, No. 76. Entire issue offered. From the library of Dean E. Wooldridge. His name in gilt lettering to lower part of spine. Very fine and clean. Pp. 749-760; 769-789.

First appearance of Feyman's landmark Quantum Electrodynamics (QED) illustrated but his famous Feynman-Diagrams which "revolutionized nearly every aspect of theoretical physics" (Kaiser, Physics and Feynman's Diagrams). The whole field of quantum electrodynamics advanced greatly because of this graphical formalism, which allowed researchers to communicate in an effective manner. Feynman, Schwinger and Tomonago shared the 1965 Nobel Prize in Physics "for their fundamental work in quantum electrodynamics, with deep ploughing consequences for the physics of elementary particles".

"At Cornell, Feynman perfected his approach to quantum theory, melding several of his prewar insights with the more pragmatic, numbers-driven approach he had honed during the war. One of his first tasks was to publish a long article, based on his dissertation, that presented a brand-new approach to quantum mechanics. Published in 1948 under the title, 'Space-Time Approach to Non-relativistic Quantum Mechanics'" in the journal Reviews of Modern Physics, his lengthy article focused on the 'Lagrangian' function for a particle, a particular combination of kinetic and potential energy familiar from classical mechanics. The probability that a quantum object would travel from one location, x1, at a time t1, to some other location, x2, at a later time t2, Feynman showed, could be calculated by summing over-that is, integrating-all of the possible paths through space and time that connected these two end points. The contribution of each path to the total would be weighted by its classical Lagrangian function evaluated along that path; hence, the technique became known as path integrals. The main difference from the standard formalism lay not in outcomes, but in conceptual approach. Werner Heisenberg and Niels Bohr had argued vehemently during the 1920s that quantum mechanics spelled the end for any type of visualization of the atomic domain. Feynman countered with an intuitive approach, built around picturing the paths of particles through space and time. His greatest success [with his Feynman-diagrams] came on the heels of this path-integral approach" (DSB).

"Feynman's two papers on QED [the two present papers] were completed in April and May 1949. In the first one, 'The Theory of Positrons,' he carefully explains the meaning of his diagrams beginning with their application to the Schrödinger equation. Application to the Dirac equation yields an interpretation of the positron in which Dirac's original hole theory is no longer needed. The second paper, 'Space-Time Approach to Quantum Electrodynamics,' contains the Feynman rules and explains their usage. By these rules, computations for specific problems are simplified so much that Schwinger, much later, said: "Like the silicon chip of more recent years, the Feynman diagram was bringing computation to the masses"" (Brandt, Harvest of a Century).

Dean Everett Wooldridge (1913 - 2006) was a prominent engineer in the aerospace industry.

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