  We apply the Liouville-von Neumann (LvN) approach to open systems to describe
the nonequilibrium quantum evolution. The Liouville-von Neumann approach is a
unified method that can be applied to both time-independent (closed) and
time-dependent (open) systems and to both equilibrium and nonequilibrium
systems. We study the nonequilibrium quantum evolution of oscillator models for
open boson and fermion systems
