# Dirac, Paul Adrien Maurice

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## Dirac, Paul Adrien Maurice

(dĭrăk`), 1902–84, English physicist. He was educated at the Univ. of Bristol and St. John's College, Cambridge, and became professor of mathematics at Cambridge in 1932. In 1928, Dirac published a version of quantum mechanics that took into account the theory of relativity**relativity,**

physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference.

**.....**Click the link for more information. (see quantum theory

**quantum theory,**

modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity together form the theoretical basis of modern physics.

**.....**Click the link for more information. ). One consequence of his theory was the prediction of negative energy states for the electron, implying the existence of an antiparticle

**antiparticle,**

elementary particle corresponding to an ordinary particle such as the proton, neutron, or electron, but having the opposite electrical charge and magnetic moment.

**.....**Click the link for more information. to the electron; this antiparticle, the positron, was discovered in 1932 by C. D. Anderson

**Anderson, Carl David**

, 1905–91, American physicist, b. New York City, grad. California Institute of Technology (B.S., 1927; Ph.D., 1930). Associated with the institute's physics department from 1930, he became professor in 1939.

**.....**Click the link for more information. . Dirac's equation for the motion of a particle is a relativistic modification of the Schrödinger wave equation, the basic equation of quantum mechanics. For their work Dirac and Erwin Schrödinger

**Schrödinger, Erwin**

, 1887–1961, Austrian theoretical physicist. He was educated at Vienna, taught at Breslau and Zürich, and was professor at the Univ. of Berlin (1927–33), fellow of Magdalen College, Oxford (1933–36), and professor at the Univ.

**.....**Click the link for more information. shared the 1933 Nobel Prize in Physics. Dirac also received the Copley Medal of the Royal Society in 1952 for this and other contributions to the quantum theory, including his formulation (with Enrico Fermi

**Fermi, Enrico**

, 1901–54, American physicist, b. Italy. He studied at Pisa, Göttingen, and Leiden, and taught physics at the universities of Florence and Rome. He contributed to the early theory of beta decay and the neutrino and to quantum statistics.

**.....**Click the link for more information. ) of the Fermi-Dirac statistics and his work on the quantum theory of electromagnetic radiation. He wrote

*The Principles of Quantum Mechanics*(1930, 4th ed. 1958).

### Bibliography

See biographies by H. Kragh (1990) and G. Farmelo (2009).

*The Great Soviet Encyclopedia*(1979). It might be outdated or ideologically biased.

## Dirac, Paul Adrien Maurice

Born Aug. 8, 1902, in Bristol. British theoretical physicist; one of the founders of quantum mechanics. Member of the London Royal Society (1930).

Dirac studied at Bristol University and then at Cambridge University, where he received his Ph.D. in 1924. In 1932 he became a professor at Cambridge University, occupying the chair that I. Newton occupied. Dirac worked on the so-called transformation theory of quantum mechanics (1926-27) and made a considerable contribution to the development of quantum statistics. In particular, he established a relation between the nature of statistical distribution and the properties of symmetry of wave functions (1925). He constructed a quantum-mechanical theory of the electron that satisfied the requirements of the theory of relativity. Dirac’s theory in a natural manner included the spin in the number of quantum-mechanical characteristics of the electron and made it possible to explain the anomalous Zeeman effect and the fine structure of the spectrum of hydrogen-like atoms. A particularly important result of Dirac’s theory was that it predicted the existence of a particle with the same mass as an electron but with a positive charge. The discovery of the positron in 1932 (later of other antiparticles) and of the processes of the annihilation and creation of pairs brilliantly confirmed Dirac’s theory. A number of Dirac’s papers are devoted to the quantum field theory (1927); in particular, he was the first to apply the method of secondary quantization (1927), which later found extensive application in theoretical physics. Dirac is a foreign member of the Academy of Sciences of the USSR (1931) and of a number of foreign academies and scientific societies. He received a Nobel Prize in 1933.

### WORKS

*The Principles of Quantum Mechanics*, 4th ed. Oxford, 1958.

“The Quantum Theory of Emission and Absorption of Radiation.”

*Proceedings of the Royal Society A*, 1927, vol. 114, no. 767, p 243.

“The Quantum Theory of the Electron.”

*Ibid*., 1928, vol. 117, no. 778, p. 610; vol. 118, p. 351.

“Théorie du positron.” In

*Rapports et discussions du Conseil physique de I’lnstitut international physique Solvay*, vol. 7. Brussels, 1934.

*In Russian translation:*

“Teoriia elektronov i protonov.”

*Uspekhifizicheskikh nauk*, 1930, vol. 10, nos. 5-6.

“Teoriia elektronov i pozitronov.” In W. Heisenberg, E. Schrödinger, and P. Dirac,

*Sovremennaia kvantovaia mekhanika: Tri nobelevskikh doklada*. Leningrad-Moscow, 1934.

*Printsipy kvantovoi mekhaniki*. Moscow, 1960.

*Lektsii po kvantovoi mekhanike*. Moscow, 1968.

*Lektsii po kvantovoi teorii polia*. Moscow, 1971.