  We investigate the exact solution, perturbation theory and master equation of
open system dynamics based on our serial studies on quantum mechanics in
general quantum systems [An Min Wang, quant-ph/0611216 and quant-ph/0611217].
In a system-environment separated representation, a general and explicit
solution of open system dynamics is obtained, and it is an exact solution since
it includes all order approximations of perturbation. In terms of the cut-off
approximation of perturbation and our improved scheme of perturbation theory,
the improved form of the perturbed solution of open systems absorbing the
partial contributions from the high order even all order approximations is
deduced. Moreover, only under the factorizing initial condition, the exact
master equation including all order approximations is proposed.
Correspondingly, the perturbed master equation and its improved form different
from the existed master equation are given. In special, the Redfield master
equation is derived out without using Born-Markov approximation. The solution
of open system dynamics in the Milburn model is also gained. As examples, Zurek
model of two-state open system and its extension with two transverse fields are
studied.
