  We have developed a novel method to describe superradiance and related
cooperative and collective effects in a closed form. Using the method we derive
a two-atom master equation in which any complexity of atomic levels,
semiclassical coupling fields and quantum fluctuations in the fields can be
included, at least in principle. As an example, we consider the dynamics of an
initially inverted two-level system and show how even such in a simple system
phenomena such as the initial radiation burst or broadening due to
dipole-dipole interactions occur, but it is also possible to estimate the
population of the subradiant state during the radiative decay. Finally, we find
that correlation only, not entanglement is responsible for superradiance.
