Topological aspects of quantum chaos

Quantized classically chaotic maps on a toroidal two-dimensional phase space are studied. A discrete, topological criterion for phase-space localization is presented. To each eigenfunction is associated an integer, analogous to a quantized Hall conductivity, which tests the way the eigenfunction explores the phase space as some boundary conditions are changed. The correspondence between delocalization and chaotic classical dynamics is discussed, as well as the role of degeneracies of the eigenspectrum in the transition from localized to delocalized states. The general results are illustrated with a particular model.     

DeWitt-Schwinger expansion for projective and Grassmann spaces

We propose a method of calculating the heat kernel expansion of coset spaces. The five first coefficients of this expansion on symmetric spaces of dimension d8 are obtained.     

An explicit form of the vertex operators in two-dimensional sl(2,ℂ)-invariant field theory

An explicit form of the vertex operators in two-dimensional sl(2,)-invariant quantum field theory is found.     

Gyromagnetic ratios of low-lying rotational states in156, 158, 160Gd

Transient-field precessions were measured simultaneously for levels in the ground-state bands of^{156, 158, 160}Gd as ions of these nuclei traversed a thin polarized Fe foil. Relative g-factors of levels up to 6 ₁ ⁺ were deduced, those of the 4 ₁ ⁺ levels being determined with greatest precision. In contrast with the conclusions of the recent report by Alzner et al. [1], our results are consistent with g(4 ₁ ⁺ ) having the same value in all three isotopes and imply g(2 ₁ ⁺ )=g(4 ₁ ⁺ ) in¹⁵⁶Gd, consistent with nuclear structure models.     

Efficient second-harmonic generation in Tl3AsSe3 using focussed CO2 laser radiation

The nonlinear material Tl₃AsSe₃ was used to convert pulsed 10.6 m laser radiation into the second harmonic. The laser beam was tightly focussed, and an energy conversion efficiency of 57% was obtained, which is the highest reported to date in the mid-IR.     

Rückstreung schneller Elektronen

The inelastic reflection of fast electrons is investigated on base of invariant imbedding method. The non-linear term in the integral equation is neglegted by means of the strong anisotropical elastic cross section of fast electrons. Using the small-angle approximation and the Laplace transformation a simple analytical formula is found expanding the backscattering coefficient into a series of Legendre polynomials. It has shown that the results from the model are in good quantitative agreement with experimental data.

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Rückstreung schneller Elektronen

Zusammenfassung Die Rückdiffusion schneller Elektronen wird mit Hilfe der Einschließungsmethode beschrieben, wobei das nichtlinere Glied in der erhaltenen Integralgleichung auf Grund der starken Anisotropie des elastischen Streuquerschnitts vernachlässigt wird. Eine einfache analytische Lösung, als Reihenentwicklung nach den Legendreschen Polynomen dargestellt, wurde im Modell kleiner Winkelstreuung und mit Hilfe der Laplace-Transformation gefunden. Es wird gezeigt, daß die erhaltenen Ergebnisse gut mit experimentellen Werten übereinstimmen.

     

Electrical resistivity in the strong-correlation limit of the emery model

On the basis of the Emery model in the limitU _d , the electrical resistivity is calculated by means of the memory function method. The inelastic scattering of oxygen holes on transverse and longitudinal antiferromagnetic spin fluctuations of copper spins is considered. Assuming a Fermi-liquid model for the dynamic spin susceptibility, the two-dimensional spin-fluctuation resistivity reveals a crossover from a quadratic to a linear temperature dependence. This may explain the normal-state basal-plane resistivity of high-T _c superconductors, in particular the observed non-linear temperature dependences.     

Symmetries of a nonassociative octonion field

Nonassociativity is studied in the presence of a symmetry group. The parameters of the Lorentz group as the group of motions of the 4-dimensional space-time are shown to remain associative, Nonassociativity appears on the level of representations of the Lorentz group. Infinitesimally, irreducible representations of the Lorentz group can be used in describing nonassociative spinors. Two types of solutions of the octonion spinor equation are studied. It is shown that these solutions can be transformed into one another only if the associator is broken according to ¦A¦=1. In addition, a new mechanism for generating electromagnetic moments of particles is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 102–106, November, 1991.     

Spectral and quantum-chemical study of some heteroanalogs of 1,4-bis(5-phenyl-2-azolyl)benzenes

The effect of structural changes in the molecules of thiophene and furan analogs of 1,4-bis(5-phenyl-2-azolyl)benzenes on their electronic spectra was studied by the MO LCAO method within the -electron approximation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 817–821, June, 1991.     

Influence of metal ions on the activity and stability of the glucose isomerase from Streptomyces atratus

The influence of a number of bivalent metals on the activity ofStreptomyces atratus glucose isomerase has been studied. Mg²⁺ ions are activators and Co²⁺ ions are stabilizers of the glucose isomerase activity. The effective kinetic parameters for the action of the enzyme have been determined.