Robert Marshak (born 11.10.1916) is an American physicist and a member of the National Academy of Sciences (1958). He was born in New York. He graduated from Cornell University (1939). In 1939-70 he taught at the University of Rochester (professor from 1949), in 1970 — 79 he was president of New York University (Stony Brook) and from 1979 professor at the Polytechnic Institute in Blacksburg (Virginia). In 1942 — 43 he worked at the Radiation Laboratory of the Massachusetts Institute of Technology, in 1943 —44 at the Montreal laboratory and in 1944—46 at the Los Alamos laboratory.
His work concerns nuclear physics and elementary particle physics, in particular meson physics and the theory of weak interaction. He studied the sources of the energy of stars and of atomic nuclei and the diffusion of neutrons. In 1940 he applied to meson pairs the idea of the interaction of nucleons through the emission and absorption of pairs of particles, and in 1947, together with H. Bethe, he predicted the existence of two different types of meson. In 1957, together with E. Sudarshan (independently of M. Gell-Mann and R. Feynman), he developed the universal theory of weak interactions, in 1959 together with S. Okubo he postulated the lepton-hadron analogy, and in 1960—61 he proposed a non-linear theory of elementary particles.