Gregory Markarovich Garibian (born 13.12.1924) is a Soviet theoretical physicist and an academician of the Academy of Sciences of the Armenian SSR (1971). He was born in Tbilisi. He graduated from Moscow University (1948). Since 1948 he has been head of a laboratory at the Yerevan Physics Institute.
His research has concerned quantum electrodynamics, astrophysics, the physics of cosmic rays and questions of the passage of charged particles through matter. He studied the bremsstrahlung of the electron and the production of pairs by a photon in the field of an electron (positron), the radiation of relativistic electrons moving in the magnetic fields of nebulae and stars, and a number of annihilation phenomena in colliding electron-positron beams. He studied the mechanisms of the electromagnetic energy losses of charged particles in matter. He proved that in thin films of matter the ionisation energy losses of fast particles proceed without the Fermi density effect. He discovered X-ray transition radiation (1959) and developed its theory. He established that the energy given up to this radiation depends linearly on the Lorentz factor of the charge. In the course of the development of the theory of this radiation many effects were taken into account, such as the influence of multiple scattering on its production and others.