Contribution of One-Time Pair Correlation Function to Kinetic Phenomena   in Nonequilibrium Gas
  It has been established in nineteen seventies that in nonequilibrium case the pair collisions generate non-zero two-particle correlations which are non-diagonal in momentum space and give the essential contribution to the current fluctuations of hot electrons. It is shown here that this correlations give also a contribution to the collision integral, i.e., to kinetic properties of nonequilibrium gas. The expression for electron energy loss rate P via phonons is re-derived in detail from this point of view. The contribution of the non-diagonal part of the nonequilibrium pair correlator to phonon-electron collision integral and to P is obtained and explicitly calculated in the electron temperature approximation. It is shown that these results can be obtained from stochastic non-linear kinetic equation with Langevin fluctuation force. Such an approach allows to formulate the simple general conditions under that a contribution of two-particle correlations might be essential in kinetics. The contribution obtained does not contain the extra powers of small gas parameter unlike the equilibrium virial decompositions. 
A. Ya. Shul'man (Institute of Radioengineering and Electronics of the   RAS, Moscow, Russia)