DIRAC, Paul (1902-84). The fundamental equations in quantum mechanics. Offprint from: Proc. Roy. Soc. A109 (1925). pp. [642]-653. WITH DIRAC'S PRESENTATION INSCRIPTION ON THE FRONT WRAPPER to fellow Cambridge physicist Francis Ian Gregory Rawlins (b. 1895).
[With:] Quantum mechanics and a preliminary investigation of the hydrogen atom. Offprint from: ibid. A110 (1926). pp. [561]-579.
Together 2 offprints, 8vo. (Both Dirac offprints lightly creased down the center, some other items a little browned, otherwise fine). Bound for Rawlins with 14 other offprints, journal numbers, etc. in buckram (binding dated July 1926 in a note on the front free endpaper); original wrappers present.
PRESENTATION COPY OF THE EXTREMELY RARE FIRST SEPARATE EDITIONS OF DIRAC'S FIRST TWO PAPERS IN QUANTUM MECHANICS. Dirac's new mechanics, which he introduced in his landmark "The fundamental equations in quantum mechanics," (1925) and elaborated in the following 1926 paper, succeeded in giving a complete formulation that was more general and useful than that of his contemporaries. For his new mechanics Dirac developed an algebra of abstract undefined "q-numbers," which have a noncommutative algebra and are strictly connected to Heisenberg's matrices and Schrödinger's operators. He introduced these "q-numbers" in his 1926 paper, "Quantum mechanics and a preliminary investigation of the hydrogen atom." This paper also contained Dirac's independently discovered solution of the hydrogen atom, published just five days after Pauli's.
Dirac's first papers marked the beginning of his stellar career in physics. He went on to develop a quantum theory of radiation (the foundation of quantum electrodynamics), and to formulate his landmark relativisitic theory of the electron, from which he predicted the existence of the positron. In 1933, shortly after the discovery of the positron, Dirac received the Nobel Prize in Physics, sharing it with Schrödinger.
Dirac was born in Bristol, England, in 1902, the son of an English mother and Swiss father. He received his B.Sc. in electrical engineering at the University of Bristol in 1921, when he was just nineteen, and spent two more years at the university studying mathematics before going up to St. John's College, Cambridge as a research student in mathematics. In 1925, at the age of twenty-three, came the first major turning point in Dirac's career: he was introduced to quantum mechanics via Heisenberg's seminal paper on matrix mechanics, "A Quantum-Theoretical Reinterpretation of Kinematics and Mechanical Relations," the galley proofs of which one of Dirac's teachers had given him to read. In this paper Heisenberg introduced a new noncommutative multiplication rule such that xy does not equal yx; after studying Heisenberg's paper for about ten days, Dirac realized that noncommutation was the essential new idea, and that it might solve the difficulties of quantum theory, which at that point required a new mechanics that would agree with classical mechanics while preserving the quantum postulates introduced by Bohr, Pauli and Born. As Dirac himself put it:
"The idea occurred to me that the commutator A times B minus B times A was very similar to the Poisson bracket which one has in classical mechanics when one formulates the equations in the Hamiltonian form. That was an idea that I just jumped at as soon as it occurred to me. . . . I went and checked what a Poisson bracket really is and found that it was as I had thought and that one could set up the connection between a Poisson bracket and a commutator. This provided a very close connection between the ordinary classical mechanics which people were used to and the new mechanics involving the noncommuting quantities which had been introduced by Heisenberg" (quoted in Segrè, X-Rays to Quarks, p. 159).
These copies of Dirac's very rare papers form part of a volume of papers on physics and other subjects bound up for F. I. G. Rawlins, a slightly older contemporary of Dirac at Cambridge. (Rawlins apparently studied physics at Cambridge-an offprint of one of his papers is included in the volume-but he later went on to write works on art conservation, in particular the use of scientific techniques such as X-rays to study the composition of paintings.) Besides the Dirac papers, the volume includes a presentation copy of the paper "On the Adjustment of Sir J. J. Thomson's Theory of Light to the Classical Electromagnetic Theory" by physicist mathematician EDMUND TAYLOR WHITTAKER (1873-1956), author of the classic History of the Theories of Aether and Electricity (1910; 1951-53). The volume also contains several other papers on physics published during the 1920s. A list of these is available on request. Segrè, X-Rays to Quarks, pp. 158-60. Van der Waerden, Sources of Quantum Mechanics, pp. 40-42; 58-59, and reprinting Dirac's two papers on pp. 307-20 and 417-27. Weber, Pioneers of Science: Nobel Prize Winners in Physics, pp. 97-98.