We use the ideas of effective medium theory to present a self-consistent decimation which yields the exact fixed point for the q-component Potts model in a square lattice and also generates the exact critical surface for anisotropic interactions.

A system of two-level atoms interacting with one mode of a quantized radiation field is considered by the quantum field theory. The existence of a phase transition to the spontaneous coherent state (SCS) is shown. This state arises from the Bose-Einstein condensation of the photons of the...

In this paper a formal MSW approach is established to calculate the energy levels of atomic clusters and molecules. It is shown that the standard secular equation is formally preserved, though the muffin-tin approximation is replaced by the only assumption that the total potential is a sum of...

On the basis of the conservation laws (or balance equations) for the continuously varying densities and currents describing a system with an interface between two bulk phases, interfacial densities and currents at the dividing surface are defined. It is shown that the dynamic behaviour of the...

Through a multiple series expansion, the stationary velocity distribution of ions in a gas in an electrostatic field is derived. Its final form is a Burnett function series times the (maxwellian) equilibrium distribution. The following assumptions are made: (1) the ions are dilutely and...

The limits of validity of the phenomenological rate equation, and the phenomenological rate constant kf and kb are found for the exchange reaction A + BC AB + C within the framework of simple multistate models. The possibility of macroscopically long transient times is discussed. The rate...

We present two examples of hamiltonian systems where ordered motions occur in spite of local exponential divergences. The conclusion is that Toda's criterion, which relies on local stability properties, cannot be used in general as a sufficient criterion to ensure stochastic behaviour of...

A slightly modified version of the Maier-Saupe model is presented. As a result of this modification, that relies on the introduction of a spherical constraint, the model can be easily solved analytically in the mean field approximation. Simple expressions result for the relevant thermodynamic...

The elements of the tensor of the susceptibility and the staggered susceptibility of a one-dimensional I Ising chain, with xx couplings between the spins are investigated in the presence of a magnetic field b parallel with or perpendicular to the x direction. Exact expressions are given for all...