Ilya Mikhailovich Lifshitz (13.01.1917-23.10.1982) was a Soviet theoretical physicist, an academician (1970; corresponding member 1960) and an academician of the Academy of Sciences of the Ukrainian SSR (1967). He was the brother of E. M. Lifshitz. He was born in Kharkov. He graduated from Kharkov University (1936) and the Kharkov Polytechnic Institute (1938). In 1937—68 he worked at the Kharkov Physico-Technical Institute (head of the theoretical department from 1941) and at the same time, from 1944, he headed a chair at Kharkov University. From 1969 he was head of the theoretical department of the Institute of Physical Problems of the USSR Academy of Sciences and from 1964 professor at Moscow University.
His research was in the field of solid-state physics, chiefly the general theory of the condensed state of matter (the dynamical theory of the crystal lattice, the electron theory of metals, the problem of the energy spectrum of disordered systems, the theory of quantum crystals, the theory of phase transitions and others). He established the connection between the observable properties of metals and the geometry and topology of their Fermi surface, put forward the idea of reconstructing the energy spectrum of condensed bodies from experimental data, and showed that such a problem can be solved. As a result, in 1954—65 Lifshitz and his pupils constructed the modern electron theory of metals (the Lenin Prize, 1967).
Lifshitz did pioneering work on the behaviour of electrons in disordered systems. He was the first to analyse the energy spectrum of crystals with defects, discovered local and quasi-local levels, and constructed the thermodynamics of layered and filamentary structures. He developed the theory of one of the basic processes of plastic deformation, the process of twinning (1948), and also the theory of the diffusional-viscous flow of polycrystalline bodies.
Much of Lifshitz's work concerned physical kinetics. He elucidated the kinetics of the destruction of the superconducting state by a magnetic field and by a current, and he was the first to trace the kinetics of phase transitions of the second kind and the kinetics of the transition of a metal from the superconducting state to the normal one under the action of a magnetic field. He constructed the theory of quantum transitions of the first kind at low temperatures. He predicted a phase transition of order 2½ (1960) and quantum diffusion (1969). He is one of the creators of the modern dynamical theory of solids and of the physics of quantum crystals. His research also concerned the statistical thermodynamics of polymers.
He founded a school of solid-state physics (A. F. Andreev, E. A. Kaner, M. I. Kaganov, A. M. Kosevich, F. G. Bass, V. V. Slyozov, V. M. Tsukernik and others). The F. Simon and L. I. Mandelstam prizes.