BBGKY (Bogolyubov, Born, Green, Kirkwood
and Yvon) hierarchy is a chain of an infinite number of integrodifferential
evolution equations for the sequence of distribution functions of particle
clustersdescribing all possible states of manyparticle systems. For
the system of finite number of particles the BBGKY hierarchy is an equivalent
to the Liouville equation in the classical case and the von Neumann
equation in quantum case.
The BBGKY hierarchy describes both equilibrium and nonequilibrium states of manyparticle systems from a common point of view. Nonequilibrium states are characterized by the solutions of initial value problem for this hierarchy and, correspondingly, equilibrium states are characterized by the solutions of the stationary BBGKY hierarchy, see [13]. In the socalled large scale limits asymptotics of solutions to the initial value problem of the BBGKY hierarchy are governed by nonlinear kinetic equations or by the hydrodynamic equations dependig on initial data. For example, in the BoltzmannGrad limit the asymptotics of the BBGKY hierarchy solutions is described by the Boltzmann hierarchy and, as a consequence, for factorized initial data the equation determining the evolution of such initial state is the Boltzmann equation. General references for this area are [15]. See also: Liouville equation, Kinetic equations, Gibbs states, BoltzmannGrad limit.
