Kimball A. Milton Bücher

Set during World War II, the narrative explores Julian Schwinger's pivotal role at MIT's Radiation Laboratory, where he focused on radar technology rather than nuclear weapons. At just 25, he sought a less structured environment, contrasting with his previous experiences in more regimented settings. The lab's work on microwave technology was crucial for the war effort, showcasing Schwinger's iconoclastic approach and significant contributions to science. His decision to join the Rad Lab reflects his preference for impactful innovation over military applications of nuclear physics.

These tutorial notes explore the evolution of quantum mechanics from stationary action principles to Schwinger's Quantum Action Principle and Feynman's path-integral formulation. Part I highlights their connection and applications, while Part II covers the variational formulation of quantum electrodynamics and source theory development.

Julian Schwinger was already the world’s leading nuclear theorist when he joined the Radiation Laboratory at MIT in 1943, at the ripe age of 25. Just 2 years earlier he had joined the faculty at Purdue, after a postdoc with OppenheimerinBerkeley, andgraduatestudyatColumbia. Anearlysemester at Wisconsin had con? rmed his penchant to work at night, so as not to have to interact with Breit and Wigner there. He was to perfect his iconoclastic 1 habits in his more than 2 years at the Rad Lab. Despite its deliberately misleading name, the Rad Lab was not involved in nuclear physics, which was imagined then by the educated public as a esoteric science without possible military application. Rather, the subject at hand was the perfection of radar, the beaming and re? ection of microwaves which had already saved Britain from the German onslaught. Here was a technology which won the war, rather than one that prematurely ended it, at a still incalculable cost. It was partly for that reason that Schwinger joined this e? ort, rather than what might have appeared to be the more natural project for his awesome talents, the development of nuclear weapons at Los Alamos. He had got a bit of a taste of that at the “Metallurgical Laboratory” in Chicago, and did not much like it. Perhaps more important for his decision to go to and stay at MIT during the war was its less regimented and isolated environment.