  A quantum-kinetic formulation of the dynamical evolution of a high-energy
non-equilibrium gluon system at finite density is developed, to study the
interplay between quantum fluctuations of high-momentum (hard) gluons and the
low-momentum (soft) mean color-field that is induced by the collective motion
of the hard particles. From the exact field-equations of motion of QCD, a
self-consistent set of approximate quantum-kinetic equations are derived by
separating hard and soft dynamics and choosing a convenient axial-type gauge.
This set of master equations describes the momentum space evolution of the
individual hard quanta, the space-time development of the ensemble of hard
gluons, and the generation of the soft mean-field by the current of the hard
particles. The quantum-kinetic equations are approximately solved to order g^2
(1+gA) for a specific example, namely the scenario of a high-energy gluon beam
along the lightcone, demonstrating the practical applicability of the approach.

High Energy Physics - Phenomenology;High Energy Physics - Theory;Nuclear Theory