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.

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.

A model for a superconductor with magnetic impurities is solved exactly on the basis of the method of approximating Hamiltonians. The model consists of a combination of the BCS model and the Zener s-d exchange interaction model. The thermodynamically equivalent Hamiltonian is constructed from...

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.

Here we propose a method of construction of the second order approximation for the ground state energy for a class of model Hamiltonians with a linear type of interaction with respect to Bose operators in the strong coupling case. For an application of the above-mentioned method we have...

The quenched Potts model with random coupling parameters and random fields is considered. These random quantities may have arbitrary distribution densities. They may be different for different pairs of sites and different sites respectively. On the basis of the Bogolubov variational principle1)...

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...

A general class of model systems of quantum statistical mechanics representing substance coupled to a discrete spectrum of a quantized boson field is studied on the basis of the “approximating (trial) Hamiltonian” method. Proof is presented that the models under investigation are exactly...

The Dicke model is investigated within and without rotating-wave approximation in the case of a lossless resonant cavity. Numerical results for the time evolution of the atomic population inversion, dipole moment and atomic and field squeezing parameters for an initial field are presented for...