A model Hamiltonian describing bosons in one and two space dimensions interacting via a repulsive interparticle potential is shown to give rise to the phenomenon of superfluidity. The model has macroscopic occupation of infinitely many single-particle quantum states and the energy spectrum of...

The time evolution for the logarithm of the probability as derived from the master equation, is expanded in terms of the inverse of the size of the system. The first term of the expansion yields the Hamilton-Jacobi equation studied by Kubo et al.7). The second term, which plays a fundamental...

The two-photon resonance fluorescence spectrum of a three-level atom is shown to consist of the low frequency modes in addition to the high frequency ones in the limit of high photon densities. The spectral function for the low frequency modes consists of two lorentzian lines describing: the...

General lower bounds for the time average CAA(∞)≡limT→∞(1T)∝T0 CAA(t) dt of the correlation CAA(t)≡〈A(t)A(0)〉−〈A〉2 of an arbitrary variable A are derived, which depend only on the temperature derivatives of the canonical averages of A and the Hamiltonian of the system. The...

The classical equations of motion of a continuum Heisenberg spin system in N dimensions are written in the form of equations for a particle field and a gauge field. Known results, such as the exact solution for N = 1 and the self-dual solution for N = 2, are recovered. Of the new results we...

We study the covariance of the Fokker-Planck equation under general gross variables transformations by means of Riemann differential geometry using an affine connection Γϱμν unsymmetric in their lower indices and without assuming that the covariant derivative of the diffusion tensor Dμν;ϱ...

In the random-bond model of Ising spins, the concept of a multiple-bond distribution of effective field was introduced in the pair approximation. The integral equation for a single-bond distribution was derived intuitively. The variational energy at T = 0 is expressed in terms of two parameters...

On the basis of an ad hoc local free energy postulate recently advanced by de Gennes and Fisher, predictions are made for the local composition/magnetization perturbations induced near a wall by the presence of a second parallel wall at finite separation D, in a system at its bulk critical...

We continue our study of the nonlinear Boltzmann equation for “diffuse” binary scattering between subsystems in a microcanonical ensemble. Exact similarity solutions of Bobylev-Krook-Wu type are found for systems of arbitrary dimensionality and in both continuous and discrete state...

Exact analytic results for the steady-state atomic correlation functions of arbitrary order n are given for a system of N superimposed two-level atoms (the Dicke model) collectively interacting with an imposed C.W. laser field. Photon statistical studies through the normalised...