Sergei Vladimirovich Tyablikov (Russian: Серге́й Влади́мирович Тя́бликов; September 7, 1921 – March 17, 1968) was a Soviet theoretical physicist known for his significant contributions to statistical mechanics, solid-state physics, and for the development of the double-time Green function's formalism.
In the period 1966–1968, Sergei Tyablikov also worked at the Joint Institute for Nuclear Research, where he was the first Head of the Statistical Mechanics and Theory of Condensed Matter Group at the Laboratory of Theoretical Physics.
During postgraduate study in 1944–1947 he worked on theory of crystallization, where he applied such methods as diagonalization of bilinear forms in Bose or Fermi operators, etc., which later became a common tool for theoretical physicists.
He was involved in the development of operator form of perturbation theory, approximate second quantization, adiabatic approximation for systems with translational invariance, and other theoretical physics methods which play an important role in the theory of many-particle systems.
In 1959, Sergei Tyablikov and Nikolay Bogoliubov published the paper [1] which strongly influenced the development of the many-body physics and specifically the quantum theory of magnetism.