Thermal and field perturbations away from the renormalization-group fixed point are considered in 2D conformal field theory. General expressions for the effective critical exponents ν, α and δ are obtained in terms of the central charge, third moment of energy and spin correlation,...

An expression of the XXZ model is given from which the Ising, isotropic XY and Heisenberg models may be more properly obtained by varying only one anisotropy parameter. The ground state and spin configuration of the antiferromagnetic quasi-classical s = 12XXZ chain in a magnetic field of...

A logistic growth model driven by additive and multiplicative noises which are correlated with each other is investigated. Using the Novikov theorem and the projection operator method, we obtain the analytic expressions of the stationary probability distribution pst(x), the relaxation time Tc,...

In this paper a multiphoton Jaynes-Cummings model in which the atom-field coupling depends on the intensity of the radiation field is introduced. The time evolution of the atomic inversion operator is obtained in the Heisenberg picture. The atomic dynamical behavior is analysed by means of...

We have investigated the evolution of the field quantum entropy and the entanglement of the atom-field in the Jaynes-Cummings model without the rotating-wave approximation, and examined the effects of the virtual-photon processes (the counter-rotating terms) on the evolution of the field quantum...