A method of partial elimination of boson variables is developed and on its basis exact hierarchies for two-photon processes in a macroscopic two-level system are obtained. The dynamics of a cascade-type process and of combination scattering processes is examined.

The theory of collective Raman scattering has been developed by using the quantum-mechanical master-equation approach and secular approximation. The influence of the frequency detuning of resonance and other parameters on the collective spectral properties of scattered light is investigated.

The resonance Raman scattering from a system of N three-level atoms that are driven by a strong laser field with the phase and amplitude fluctuations is considered. The exact on-resonance steady-state solution to the atomic density matrix is obtained. The collective properties of the fluorescent...

An exact kinetic equation for a three-level macroscopic system interacting with an electromagnetic field is obtained taking into account the coherent pumping processes. On its basis the collective spontaneous radiation of the system is examined in the markovian limit. The relations between the...

An exact hierarchy for the Dicke-type model problems is obtained. On its basis spontaneous-radiation processes are examined.

We use the Hermitian phase formalism of Pegg and Barnett to study phase properties of a coherent field interacting with a cooperative system. We show that if the number of eigenvalues in a subspace with fixed photon number n is large, as the evolution proceeds, the phase probability distribution...

The influence of a classical external field and a classical current on the character of the dynamic process in a superfluorescent system is investigated. It is shown that a constant current does not affect the characteristics of a superfluorescent pulse. The effect of “locking” the residual...

An exactly soluble model of a ferromagnet with paramagnetic fluctuations is analysed both analytically and numerically. The existence of such fluctuations depends on a relation between the direct and exchange interactions of particles. The presence of these fluctuations can drastically influence...