General metric tensors invariant under some maximal subgroups of the conformal group of space-time are determined through an infinitesimal method based on conformal point transformations (discussed by Fulton, Rohrlich and Witten). The cases of the following maximal subgroups are successively...

Bound two-magnon states cannot exist in the XY-spin model with an arbitrary radius of bilinear exchange interaction, S ⪖ 12. In the Ising model with bilinear and biquadratic interaction, however, as well as in every anisotropic model at κ = π, the bound states number is n + 1 (n at S =...

Mode-mode coupling theory is used to obtain the t−52 long time tails for the spin and energy densities autocorrelation functions and the related Kubo integrands for a Heisenberg magnet in the high temperature approximation.

The “spin-clock” method proposed by Baz' to derive formulae for the duration of scattering processes in a stationary context is discussed. The formulae proposed by Baz' show discrepancies with the work of other authors, consisting of certain oscillatory terms. In other types of approach...

The behavior of decaying atomic states in applied fields is studied. Corrections to expected line shapes of order α3Z2 are found and calculated for the hydrogen n = 2 system.

Ising-like models on a square lattice are studied by real space renormalization transformations in which the cells are confined to sublattices. A general class of transformations is discussed which maps all ground states that are invariant under translation over n lattice constants onto...

The relative motions of particles in a simple liquid may be described as one-dimensional radial diffusion in an effective potential of the mean force. This effective potential may be obtained by an iteration procedure with the Vineyard approximation as the initial step. Using a harmonic...

The pair correlations in a fully ionized dilute and homogeneous hydrogen plasma in equilibrium are calculated down to r = 0 on the basis of the equilibrium hierarchy of statistical mechanics and the linear superposition approximation. Thereby the Coulomb potential between electron and proton is...

A general class of model systems of quantum statistical mechanics representing substance coupled to a discrete spectrum of a quantized boson field is studied on the basis of the “approximating (trial) Hamiltonian” method. Proof is presented that the models under investigation are exactly...

Two basic ideas about the nature of the gas-liquid transition were voiced around 1870: that in the supercritical state, vapor and liquid are indistinguishable (Andrews), and that condensation and critical behavior can be understood on the basis of a simple assumption about molecular interaction...