Early quantum electrodynamics

Covering the years 1927 to 1938, this volume traces how quantum electrodynamics took shape, beginning with P. A. M. Dirac's 1927 quantization of the electromagnetic field. The theory sat at the forefront of physics throughout this decade, and the book follows its growth from the early ideas to the edge of renormalization theory.

The introductory Frame-Setting Essay, together with the classic papers reprinted alongside it, highlights the shifts in concepts that led physicists toward that threshold. The central figures are Niels Bohr, Dirac, Werner Heisenberg and Wolfgang Pauli, the same thinkers whose attention to foundational questions had produced quantum mechanics. They carried over tools that had worked well in that earlier effort, including reworked notions of intuition and correspondence-limit arguments, and tried to build a quantum theory compatible with special relativity and gauge invariance that could describe light interacting with electrons without divergences. The effort also gave rise to theoretical nuclear physics. The book asks why a properly renormalized version of the theory arrived so late, given Freeman J. Dyson's 1949 claim that no new ideas or techniques were needed, and it uses the published papers and correspondence of Bohr, Dirac, Heisenberg and Pauli to examine what a scientific theory means and how it is structured. The postwar, divergence-free formulation by Sin-Itiro Tomonaga, Richard P. Feynman and Julian Schwinger is part of this story.

The book also looks forward to present-day physics. Quantum electrodynamics became the model for elementary particle research, and its success paved the way for quantum chromodynamics and the unification of electromagnetic and weak interactions. Physicists have noticed that its calculational methods, such as effective Lagrangians, resemble those used in chromodynamics. Some key early papers had never appeared in English, which slowed the recognition of their implications, and several of them are reproduced here. The author suggests that work from some sixty years ago may still offer guidance for future research.