A two-level atom is enclosed in a one-dimensional box. The size of this box, as seen by the atom, is different for the two levels. In addition there is a constant field, which causes transitions between the two states. The Schrödinger equation for this system cannot be solved analytically, but...

An ion with internal degrees of freedom can be excited or deexcited when it is accelerated by an electric field and then suddenly reflected by a plane surface. When tthe internal motion is described by a single oscillator, the system is simple enough to allow the calculation of a large number of...

By numerical and analytical investigations we show that the bond-moving transformation of Migdal for planar spins on a two-dimensional lattice possesses a very rich structure. We find an infinite hierarchy of one-, three- and higher-dimensional fixed spaces. In addition to phase transitions of...

We consider two- and three-dimensional lattices with on each lattice a D-dimensional classical spin-vector. We restrict ourselves to nearest neighbour interactions which only depend on the angle between the spin-vectors. For these systems the bond-moving approximation of Migdal and Kadanoff is...

In continuation of previous work we study the energy of infinite one-dimensional systems of particles interacting with the two-body potential ϕ (x) = (1 + x4)−1. We know beforehand that not for all values of the mean volume per particle a the equidistant configuration has minimum energy among...

Using a previously described relativistic quantum theory for two particleswe calculate the spectrum of bound states of an electron in Coulomb interaction with a heavy ion change Z.

Using a Corner-type potential for the interaction between two monoaxial molecules, a simple equation has been derived for the angular dependence of the single particle distribution function. We investigate this equation for values of the molecular parameters not considered before. The usual...

When a medium energy neutron hits a free atom there is a finite probability that as a consequence of the recoil the atom becomes excited or ionised. For the simple case of a hydrogen atom exact calculations are reported of the transition probabilities for various initial and final states as a...

An integrable SU(3) soin chain equation is constructed. An explicit form of the Lax-pair representation is given and it is shown to be gauge equivalent to a set of nonlinear Schrödinger- type equations for three complex variables.