# Andronov, Aleksandr Aleksandrovich

# ANDRONOV, ALEKSANDR ALEKSANDROVICH

(*b*. Moscow, Russia, 11 April 1901; *d.* Gorky, U.S.S.R., 31 October 1952)

*theoretical physics*.

The son of an office worker, Andronov graduated from secondary school in 1918 and immediately went to work in a factory. He subsequently joined a military supply detachment, with which he traveled to the Urals. In 1920 he enrolled at the electrotechnical faculty of the Moscow Higher Technical, School, transforming to Moscow University three years later. He graduated from the physical mathematical faculty in 1925; his specially was theoretical physics. As a student he had shown great interest in theoretical mechanics and had begun to teach mechanics and theoretical physics at the Second Moscow University (now the V. I. Lenin Padagogocal Institute) in 1924. From 1926 to 1929 he was a postgraduate student at Moscow State University.

L. I. Mandelshtam played a major role in Andronov’s development as a physicist. Under his guidance Andronov did his first scientific research, which was related to the theory of the scattering of light by a fluctuating liquid surface and undertook a series of studies on perturbation theory. Even after Andronov had achieved recognition and a school had evolved around him, he continued to work closely with Mandelshtam.

Although Andronov was trained as a theoretical physicist, his major field of activity was rather removed from what theoretical physicists usually studied. Attracted by atomic physics, he began to study statistical quantum physics in the late 1920’s, By 1930 his theoretical work was concentrated on the generation of oscillations, a subject to which great importance had been given by the development of the electron tube. Almost all of his subsequent research was a development of the ideas presented in his dissertation, which dealt with extremal Poincare cycles and oscillatory theory.

In 1931 Andronov moved to Gorky and worked at the university there for the rest of his life. He was also involved in the activities of the Institute of Automation and Tele mechanics of the Academy of Sciences of the U.S.S.R. and became an active member of the Academy in 1946.

Andronov’s basic works concerned oscillation theory and automatic control theory. They laid the foundations for the subsequent mathematical treatment of oscillatory process in nonlinear automatic systems that were based on the work of Poincare and on Lyapunlov’s fundamental research on the theory of stability of motion. Especially fruitful were the ideas that Andronov developed in 1928 on the ways of examining undamped oscillations in nonlinear automatic systems. Andronov called such oscillatory processes autooscillations, a term that has become generally accepted, and his works led to the development of the basic methods of the theory of nonlinear oscillations. After Andronov related nonlinear oscillations to the qualitative theory of differential equations, there was an intensive development both of the mathematical methods and of the physical applications of the theory of nonlinear oscillations. Andronov’s book on the theory of oscillations (1937), written with S. E. Khaykin, has become the basic work in the Soviet Union on nonlinear perturbation theory and has been used extensively in training specialists in this branch of radiophysics.

Andronov’s school contributed substantially to the development of the theory of automatic control. His works in this area are the direct continuation and completion of Vyshnegradsky’s O *regulyatorakh pryamofgo deystvia* (“On Regulators of Direct Action,” 1876). He also wrote on the works of Maxwell, Vyshnegradsky, and A. Stodola in the regulation of machines.

Many of Andronov’s students continued his research in the theory of oscillations, the dynamics of machines, and the qualitative theory of differential equations and developed his scientific ideas, rendering them accessible to a wide circle of physicists and mathematicians.

## BIBLIOGRAPHY

I. Original Works. Andronov’s wittings include *Teoria kolebany* (“Theory of Oscillations”); Moscow Leniongrad,1937), written with S.E.Khaykin; and So *branie trudov* (“Collected Works” ;Moscow, 1956).

II. Secondary Literature. See the obituary in *Vestnik Akademii nauk***SSSR,22,** no.12 (1952),81; and *pamyati A.A Andronova* (“Recollectionsb of A.A.Andronov; Moscow, 1955), a collections that includes an annotated list of Andronov’s works.

A. T. Grigorian

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