We discuss the effects of hydrodynamics on the molecular derivation of the phenomenological Langevin equation. When the mass and density of the brownian particle are sufficiently large compared to the corresponding bath variables, the phenomenological equation is obtained. If, in addition, the...

The adiabatic perturbation formalism is used to derive several alternative expressions for the effective Hamiltonian of a discrete energy level. It is shown how in the nondegenerate case these expressions may be cast in the form of linked-cluster expansions. The connection between the energy...

In this paper a low-energy-electron diffraction theory for molecular crystals is presented. The influence of the bilk Frenkel excitons on the intensity of the non-specular beams is studied, the (00) beam being considered in a previous paper.

Recent analyses of fluctuations in non-equilibrium systems by Prigogine, Malek-Mansour and Nicolis have indicated the existence of a minimal coherence length beyond which fluctuations can amplify and induce instabilities at a macroscopic scale. Conversely, this observation suggests the emergence...

It is pointed out that the method of functional integration provides a very convenient starting point for the renormalization group approach to the interacting Bose gas. Using such methods we show in a general and non-perturbative way that the critical exponents of the Bose gas are identical to...

A comprehensive theory of the transverse dielectric function, light absorption and other aspects of photon propagation as well as level shifts, the chemical potential and statistical mechanics of hydrogenic fluids ranging from the fully ionized plasma to the atomic fluid, is presented. A Coulomb...

The existence of the thermodynamic limit is proved for the random one-dimensional Ising systems under the assumption that the interaction energies are random variables taking on continuous values and the distribution of the random variables is given by a continuous function. It is assumed that...

The SAW-approximation is calculated for the quantum-mechanical XY-model for spin 12 in a parallel magnetic field. For this purpose we derive an exact expression for the internal weight factors of the polygon graphs.

Time-dependent properties of the one-dimensional XY model with Dzyaloshinsky interactions in the presence of a magnetic field in the z direction are investigated. Explicit expressions are derived for the time correlation functions of the z components of two spins and the time auto-correlation...

The dielectric alignment of a dilute non-polar component in a polar solvent may be determined by NMR spectroscopy. In this paper a series expansion of the alignment up to second order terms in the dipolar interaction is presented for a non-polar molecule replacing a single polar molecule in a...