Collisions between atoms through the intermediary of zero sound wave of finite lifetimes are discussed to account for the memory effect on the density correlations of atoms. The second-quantization formalism is used to describe the formation and decay of zero sound, and a new non-markovian...

The theory developed in an earlier paper is applied to the degenerate Bose fluid at very low temperatures. It is seen that the transformation functions A(k), B(k), and C(k) can be chosen in such a way that the expansions of the grand potential and the momentum distribution are well-behaved at...

Methods are described to determine the isotropic as well as the anisotropic part of the Knight shift from powdered samples of several V3X compounds (V3Co, V77.5Ni22.5, V3Rh, V3Pd, V3Pt and V3Ir). Measurements of the Knight shifts of the central line as well as the satellites prove to be...

A diagrammatic technique for spin and pseudospin lattice systems with complicated single- body levels is developed using the generalized Pauli operators. Rules for the construction and evaluation of the diagrams, representing the zeroth-order many-point irreducible Green's functions are given....

We report computer simulations of collision-induced light absorption in a two-dimensional Lorentz gas over a range of densities, which we compare with theories of the intracollisional spectrum, intercollisional interference, and pressure narrowing. The theory of Lewis and Van Kranendonk...

A simple model of electrons interacting with photons which displays a metal-insulator phase transition in the case of s.c. and b.c.c. tight-binding bands is studied. A proof is given that the model is exactly solvable in the thermodynamic limit.

Explicit expressions for the time-dependent spin correlation functions are derived for the one-dimensional alternating XY-model in zero field. The ergodic properties of the wave-number dependent magnetization are discussed. It is found that the magnetization is ergodic, apart from exceptional...

The Asano-Ruelle method is used to discuss the zeroes of the partition function of arbitrary lattice systems with constraints. The group structure associated with these systems yields necessary and sufficient conditions to build up the partition function by Asano contractions. For a large class...

The thermodynamic properties of spin-one Heisenberg ferromagnets with uniaxial and biaxial anisotropy are investigated in the molecular field approximation (MFA) and random phase approximation (RPA). In MFA a full phase diagram comprising three lines of bicritical points, is obtained.

We evaluate the complete diffusion matrix describing the translation and rotation of two spherically symmetric polymers in hydrodynamic interaction in a viscous fluid. Explicit results in terms of a series expansion in inverse powers of the distance l between centers is obtained by a method of...