Vacuum-field Rabi oscillations of atoms in a cavity

The quantum electrodynamics of an atom in a cavity is reexamined from the view point of the vacuum-field Rabi oscillations. Many features of such oscillations in a single atom as well as in a cooperative system are discussed. Various physical quantities that carry the signature of these vacuum-field oscillations are calculated. Even oscillator systems are shown to exhibit such vacuum-field Rabi oscillations, which is in contrast to the external-field-induced Rabi oscillations. Such oscillations are found to occur in situations involving both single-photon and multiphoton transitions.