Sergei Natanovich Bernshtein

Born Feb. 22 (Mar. 5), 1880, in Odessa; died Oct. 26, 1968, in Moscow. Soviet mathematician. Academician of the Academy of Sciences of the USSR (1929; corresponding member, 1924) and of the Academy of Sciences of the Ukrainian SSR (1925).

From 1907 to 1933, Bernshtein taught at the University of Kharkov (from 1920, as professor), and from 1933 to 1941 he was professor at the Leningrad Polytechnic Institute and Leningrad State University. In 1935 he began working at the Mathematical Institute of the Academy of Sciences of the USSR. He was a foreign member of the Paris Academy of Sciences (1955) and other foreign scientific institutions. His primary works were devoted to the theory of differential equations, the theory of functions, and probability theory. Bernshtein found the conditions of analyticity of solutions to second-order elliptic- and parabolic-type equations and developed new methods of solving boundary-value problems for nonlinear elliptic equations. Continuing and developing the ideas of P. L. Chebyshev on the approximation of functions by polynomials, Bernshtein and his students created a new branch of the theory of functions—the constructive theory of functions. He developed the first (1917) axiomatics in the theory of probability and continued—and in a certain respect completed—the Chebyshev-Markov St. Petersburg school’s investigations of finite theorems. He also developed a theory of weakly dependent quantities, studied stochastic differential equations, and pointed out a number of applications of probabilistic methods in physics, statistics, and biology. Bernshtein received the State Prize of the USSR in 1942 and was awarded two Orders of Lenin, the Order of the Red Banner of Labor, and various medals.