Published online by Cambridge University Press: 01 April 2022
1. Introduction Dirac's (Dirac 1928) theory of the electron was the first widely accepted relativistic quantum theory, and it later provided the basis for constructing the modern electromagnetic theory of quantum electrodynamics (QED). Whereas Dirac's theory in its simplest form describes relativistic freely-propagating massive non-chiral particles of spin-½, QED describes how such particles interact with one another electromagnetically, via a dynamical quantum field.
We are grateful to Hughan Ross for helpful discussions.
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