  Two noninteracting atoms, initially entangled in Bell states, are coupled to
a one-mode cavity. Based on the reduced non-perturbative quantum master
equation, the entanglement evolution of the two atoms with decay is
investigated beyond rotating-wave approximation. It is shown that the
counter-rotating wave terms have great influence on the disentanglement
behavior. The phenomenon of entanglement sudden death and entanglement sudden
birth will occur.
