Spartak Timofeyevich Belyaev (born 27.X.1923) is a Soviet theoretical physicist and academician (1968; corresponding member 1964). He was born in Moscow. He graduated from Moscow University (1952). In 1952-62 he worked at the I. V. Kurchatov Institute of Atomic Energy; in 1962-78 he was head of a laboratory and then head of a department at the Institute of Nuclear Physics of the Siberian Branch of the USSR Academy of Sciences, and at the same time, from 1965, rector of Novosibirsk University. From 1978 he has been director of a division of the I. V. Kurchatov Institute of Atomic Energy.
His work concerns the theory of relativistic plasma, the quantum theory of many-body systems and the theory of the nucleus. He studied the properties of interacting particles obeying Bose–Einstein statistics and was the first to develop the diagram technique for Bose systems, proposing general methods of treating such systems.
Together with others he is developing the superfluid model of the nucleus. He calculated the moments of inertia of deformed nuclei, found the frequencies of quadrupole vibrations and established the conditions under which the deformation of nuclei arises.
He is the author of a number of methods for calculating collective excitations in nuclei (the adiabatic approximation for the collective Hamiltonian, boson expansions, the generalised density matrix). He discovered new types of collective excitation in the nucleus (specific pairing fluctuations, spin-orbit vibrations).