Electroweak theory, a unified field theory that describes two of the fundamental forces in nature, electromagnetism (see electromagnetic radiation) and the weak interaction. The electroweak th...

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...

Information theory or communication theory, mathematical theory formulated principally by the American scientist Claude E. Shannon to explain aspects and problems of information and communicat...

Transfinite number, cardinal or ordinal number designating the magnitude (power) or order of an infinite set; the theory of transfinite numbers was introduced by Georg Cantor in 1874. The card...

Kinetic-molecular theory of gases, physical theory that explains the behavior of gases on the basis of the following assumptions: (1) Any gas is composed of a very large number of very tiny pa...

Galois, Évariste, 1811–32, French mathematician. At the age of 17 he had evolved original concepts on the theory of algebra. He made important contributions to the theory of equations, the the...

Ramanujan, Srinivasa, 1889–1920, Indian mathematician. He was a self-taught genius in pure mathematics who made original contributions to function theory, power series, and number theory with ...

Personality, in psychology, the patterns of behavior, thought, and emotion unique to an individual, and the ways they interact to help or hinder the adjustment of a person to other people and ...

Fermat, Pierre de, 1601–65, French mathematician. A magistrate whose avocation was mathematics, Fermat is known as a founder of modern number theory and probability theory. He also did much to...

Hermite, Charles, 1822–1901, French mathematician. A professor at the École polytechnique, Paris (1869–76), and at the Faculty of Sciences (1869–97), he exerted a strong influence on the Frenc...