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THE BIRTH OF QUANTUM ELECTRODYNAMICS. First edition, extremely rare offprint, of Dirac s quantum theory of the electromagnetic field, which for the first time reconciled the wave and particle nature of light. "This paper marks the birth of quantum electrodynamics. In his Introduction and Summary, Dirac noted that the new quantum theory, based on non-commuting dynamical variables, was by then sufficiently developed to form a fairly complete theory of any dynamical system composed of a number of particles with instantaneous forces acting between them, provided it is describable by a Hamiltonian function. But hardly anything had been done up to the present on quantum electrodynamics. The questions of the correct treatment of a system in which the forces are propagated with the velocity of light instead of instantaneously, of the production of an electromagnetic field by a moving electron, and of the reaction of this field on the electron, have not yet been touched. In addition there is a serious difficulty in making the theory satisfy all the requirements or the restricted principle of relativity
Gregor Wentzel, who contributed significantly to the development of quantum electrodynamics during the 1920s, commented in 1959: Today the novelty and boldness of Dirac s approach to the radiation problem may be hard to appreciate
there had been no possibility within the correspondence principle framework to understand the process of spontaneous emission or the disappearance of a photon. Dirac s explanation
came as a revelation
In his paper, Dirac dealt with the problem of an atom interacting with the radiation field in two distinct ways that can be characterized as the corpuscular and the wave approaches. In the corpuscular approach, the light quanta are described as an assembly of non-interactive particles moving with the speed of light and satisfying the Einstein-Bose statistics
In the last brief section of his paper, Dirac turned to the interaction of an atom with the electromagnetic field as described from the wave point of view
In a lecture on the origin of quantum field theory in 1982, Dirac characterized the two approaches as follows: Instead of working with a picture of the photons as particles one can use instead the components of the electromagnetic field. One thus gets a complete harmonizing of the wave and corpuscular theories of light. One can treat light as composed of electromagnetic waves, each wave to be treated like an oscillator; alternatively, one can treat light as composed of photons, the photons being bosons and each photon state corresponding to one of the oscillators of the electromagnetic field. One then has the reconciliation of the wave and corpuscular theories of light. They are just two mathematical descriptions of the same physical reality" (Schweber, pp. 23-31). "Dirac s approach was instantly welcomed as the first consistent quantum theory of radiation and accepted as the paradigm in a whole series of subsequent studies" (Kojevnikov, p. 232). "Salam and Wigner, in their preface to the Festschrift that honored Dirac on his seventieth birthday and commemorated his contributions to quantum mechanics, succinctly assessed the man. Dirac is one of the chief creators of quantum mechanics
Posterity will rate Dirac as one of the greatest physicists of all time
He is a legend in his own lifetime and rightly so " (ibid., pp. 11-12). Not on OCLC, no copies in auction records. Provenance: Bertha Swirles (1903-99) (signature on front wrapper, marginal pencil annotations including an equation in the lower margin of p. 261). As an undergraduate at Cambridge Swirles attended lectures by J. J. Thomson and Rutherford. She remained at Cambridge in 1925 to undertake research in mathematical astronomy under the supervision of Ralph Fowler; another of Fowler s research students, a couple of years ahead of Swirles, was Paul Dirac. After periods at Bristol, Imperial College, London, and Manche.
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