Lattice electrons on a cylinder surface in the presence of rational magnetic flux and disorder

We consider a disordered two-dimensional system of independent lattice electrons in a perpendicular magnetic field with rigid confinement in one direction and generalized periodic boundary conditions (GPBC) in the other direction. The objects investigated numerically are the orbits in the plane spanned by the energy eigenvalues and the corresponding center of mass coordinate in the confined direction, parameterized by the phase characterizing the GPBC. The Kubo Hall conductivity is expressed in terms of the winding numbers of these orbits. For vanishing disorder the spectrum of the system consists of Harper bands with energy levels corresponding to the edge states within the band gaps. Disorder leads to broadening of the bands. For sufficiently large systems localized states occur in the band tails. We find that within the mobility gaps of bulk states the Diophantine equation determines the value of the Hall conductivity as known for systems with torus geometry (PBCs in both directions). Within the spectral bands of extended states the Hall conductivity fluctuates strongly. For sufficiently large systems the generic behavior of localization-delocalization transitions characteristic for the quantum Hall effect are recovered.     

Decomposition and simulation of sequential dynamical systems

Sequential dynamical systems have been developed as a basis for a theory of computer simulation. This paper contains a generalization of this concept. The notion of morphism of sequential dynamical systems is introduced, formalizing the concept of simulating one system by another. Several examples of morphisms are given. Using the morphism concept, it is shown that every sequential dynamical system decomposes uniquely into a product of indecomposable systems.     

Zur Berechnung Stekloffscher Eigenwerte-numerische Beispiele

Zusammenfassung Es werden Ergebnisse numerischer Experimente bei der Berechnung des ersten nichttrivialen Stekloff Eigenwertes angegeben.Alle Beispiele zeigen eine Monotonieeigenschaft des Eigenwertes und stützen eine Vermutung über Eigenwerte konvexer Außengebiete.

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Results of numerical experiments are given for the evaluation of the first nontrivial Stekloff eigenvalue.All examples show a monotonicity property of the eigenvalues and support a conjecture of eigenvalues for convex exterior domains.

     

Die Dimensionsfunktion von Punktmengen

Ohne Zusammenfassung     

Magneto-optic study of the critical region of EuS

Critical exponents of the insulating ferromagnet europium sulfide are determined using the technique of Faraday rotation. Values obtained are γ = 1.06 ± 0.05, β = 0.335 ± 0.01, δ = 4.20 ± 0.1 and T_c = 16.52 ± 0.02 K. The data are found consistent with the scaling hypothesis.     

Energy transfer processes in two different bifluorophoric laser dyes

The mechanism of intramolecular energy transfer in two bifluorophoric laser dyes has been investigated by measurements of laser parameters, excited state absorption and phosphorescence spectra. The new value found for the dimethyl-POPOP triplet energy (48.0 kcal/mole) accounts for the different behaviour of the two classes of bifluorophoric dyes used in this investigation.     

Equilibrium charge-state fractions for 2.7–31 keV deuterium atoms and ions in strontium vapor

Equilibrium charge-state fractions of 2.7–31 keV deuterium in strontium vapor are reported. The energy dependence of the D^- equilibrium yield is discussed. The results are compared with the D^- yield in cesium and magnesium vapors.