The theory of the irreducible many-point Green's functions, describing spin and pseudospin lattice systems, is formulated with the help of the generating functional approach. The diagrammatic technique for the generating functional is also developed. Special attention is paid to the construction...

The leading term of the exchange quantum correction to the free energy of a dense one-component plasma is computed in the near-classical limit. Two-body exchange is dominant. The path-integral method is used in its semi-classical limit. The exchange free energy is found to be exponentially small.

The effects of tri-linear modes on transport coefficients is illustrated by explicit calculations for the self-diffusion constant. In two dimensions the form of the asymptotic time behavior of the velocity autocorrelation function is changed from t-1 (bilinear modes) to (t log t)-1 (trilinear...

The concept of the average force potentials is used to develop the truncation procedure for an arbitrary equation of the chain. The closed system of integral equations for the average force potentials is formulated. In the case when the truncation approximation involves the four-particle...

A systematic theory of multiple scattering is given for a nonpolar fluid of point dipoles. Local-field correction factors are consistently accounted for to all orders. To first order (single scattering) Einstein's result is obtained; the theory yields, however, automatically to this order the...

A quantum-mechanical theory of describing systems far from equilibrium is developed. A set of time evolution equations for every moment of macroscopic variables is derived with the aid of the new idempotent operator. From this set of equations nonlinear but closed equations for the first and the...

The Friedrichs model of an unstable particle provides us with a non-trivial example of a dynamical system with a continuous spectrum. The non-unitary transformation operator which leads in our approach to a semi-group description of the time evolution of the system has been constructed in...

Exact expressions are derived for the time-dependent correlation functions of the x and y component of the magnetization for the one-dimensional anisotropic XY-model (S=12) in zero field in the high-temperature limit. As a corollary, the correlation functions for the Ising chain in a transverse...

Measurements of the diffusion coefficient of Kr in Xe at T = 298 K and in the density range 0–200 amagat are reported. The data are analyzed in order to investigate whether a logarithmic divergence appears in the density expansion of the diffusion coefficient. This analysis shows that a power...

We establish the kinetic equation for the two-spin time-dependent correlation function in the Weiss limit. Considering this equation in the limit of small wavenumbers, we obtain an explicit expression for the energy diffusion coefficient. We also discuss some difficulties connected with...