Quantum Electrodynamics and Meson Theories. Notes on the Lectures by Professor Richard P. Feynman, Cornell University. Given at the California Institute of Technology, Pasadena, California, February 6 to March 2, 1950. Prepared by Carl W. Helstrom and Malvin A. Ruderman

FEYNMAN'S UNPUBLISHED LECTURES ON MESON THEORY. First and only edition, extremely rare, of the mimeographed notes of Feynman's lecture course on meson theory, delivered as a visiting lecturer at Caltech (to which he moved permanently in the following year). Feynman had developed his distinctive diagrammatic approach while attempting to solve the problem of divergences in quantum electrodynamics (QED), the quantum theory of the interactions between electrically charged particles and the electromagnetic field (between electrons and photons, for example). "What captured most theorists' attention soon after the war was not electron physics, but rather the embarrassment of riches suddenly pouring forth from the new accelerators. A flood of new particles, similar to but in many ways distinct from the familiar electrons and photons, surprised physicists when they began to probe high-energy interactions with the aid of accelerators, rather than relying only upon cosmic rays. As quickly became clear, the new particles - dubbed 'mesotrons' or 'mesons', since the masses of many of them were intermediate between electrons and protons - interacted with each other differently than electrons and photons did" (Kaiser, p. 57). Feynman became interested in meson theory while he was still perfecting his understanding of QED, but his ideas in this area remain unpublished (see below) - these notes are thus a key historical record of Feynman's work on meson theory. Appearing 13 years before his famous three-volume Lectures on Physics, these particular notes were never published again, either separately or as part of his Selected Papers. They were probably produced in very small numbers for the graduate students and fellow faculty members who attended this advanced course. Widely regarded as the most brilliant, influential, and iconoclastic figure in theoretical physics in the post-World War II era, Feynman shared the Nobel Prize in Physics 1965 with Sin-Itiro Tomonaga and Julian Schwinger "for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles." "Mark Kac, the eminent Polish-American mathematician, wrote: 'In science, as well as in other fields of human endeavor, there are two kinds of geniuses: the 'ordinary' and the 'magicians'. An ordinary genius is a fellow that you and I would be just as good as, if we were only many times better. There is no mystery as to how his mind works. Once we understand what he has done, we feel certain that we, too, could have done it. It is different with magicians . the working of their minds is for all intents and purposes incomprehensible . Richard Feynman [was] a magician of the highest caliber'" (Biographical Memoirs of Fellows of the Royal Society of London 48 (2002), p. 99). Not on OCLC. We are not aware of any other copy having appeared in commerce. Provenance: Kenneth Hedberg (signature on title). Hedberg (1920-2019) graduated from Oregon State College (BS, 1943) and the California Institute of Technology (Ph. D., 1948), having studied chemistry at both institutions. While at Caltech, Hedberg studied under Verner Schomaker and interacted frequently with Linus Pauling. In 1956 Hedberg returned to Oregon State College where he joined the faculty of the chemistry department. Hedberg was elected a fellow of the American Physical Society and the American Association for the Advancement of Science. He was also elected to membership of the Norwegian Academy of Science and Letters. At the end of the 1940s, physics was undergoing an extraordinary period of turmoil. "Newly discovered elementary particles, mesons and the like, were proliferating madly in the newly built particle accelerators. The elementary particle physics zoo was becoming embarrassingly crowded, so crowded in fact that it wasn't clear which of the new blips on chart recorders and new tracks in bubble chambers might really represent new elementary particles and which were simply.…