Acta Physica Slovaca 50(2000)

M. Šašura
Decoherence and Milburn dynamics of open systems: The case of the linear coupler
Acta Physica Slovaca 50, 199 (2000)
Abstract: Within the framework of the Milburn model of the intrinsic decoherence [G.J.Milburn, Phys.Rev. A44, 5402 (1991)] which is based on the assumption of the existence of the fundamental time step we study the dynamics of the linear coupler. We show that the evolution governed by the Milburn equation can be significantly modified compared to the standard quantum mechanics. Dicsussion about closed systems is also included.

M. Štefaník, J. Horský
The KerrSchild Ansatz for the Nairai spacetime and the generating conjecture
Acta Physica Slovaca 50, 213 (2000)
Abstract: We will show that the Nariai metric, i.e. the static spherically symmetric vacuum spacetime with a cosmological constant, admits a conformally KerrSchild spacetime representation. We find the vacuum solutions of the EinsteinMaxwell equations for the Nariai metric using the HorskýMitskievich generating conjecture.

Z. Stuchlík
Spherically symmetric static configurations of uniform density in spacetimes with a nonzero cosmological constant
Acta Physica Slovaca 50, 219 (2000)
Abstract: Interior solutions of Einstein's equations with a nonzero cosmological constant are given for static and spherically symmetric configurations of uniform density. The metric tensor and pressure are determined for both positive and negative values of the cosmological constant. Limits on the outer radius of the interior solutions are established. It is shown that, contrary to the cases of the limits on the interior Schwarzschild and ReissnerNordström solutions with a zero cosmological constant, these limits do not fully coincide with the conditions of embeddability of the optical reference geometry associated with the exterior (vacuum) Schwarzschildde Sitter spacetime.

I. Glesk, R.J. Runser, KungLi Deng, P.R. Prucnal
100Gbits/s computer optical interconnect
Acta Physica Slovaca 50, 229 (2000)
Abstract: An experimental demonstration of an error free 100Gbit/s optical time division multiplexing (OTDM) broadcast star computer interconnect is presented. A highly scalable novel node design provides rapid interchannel switching capability on the order of the single channel bit period (1.6 ns).

N. Milinski, E. Milinski
The DC electrical conductivity calculation purely from the dissipative component of the AC conductivity. I. General formula derivation
Acta Physica Slovaca 50, 235 (2000)
Abstract: The crucial item on which the whole advance in the present work rests is the recognition that the dc conductivity of real metals (those with scatterers) can be defined as the limit , where is the real (dissipative) component of the complex conductivity , , by expelling , the imaginary (nondissipative) component of the linear response formula for electrical conductivity (Kubo formula) at the very start. It has been achieved by applying a specific rule of performing the limits , where and s are the real and imaginary part of the complex frequency z, . The specific rule by which the limits should be performed in order to keep up the dissipative and the nondissipative character of and respectively in the procedure of calculation, has been proved here in the form of a necessary and sufficient condition. This condition prescribes to take the limit before in order to expel from the nondissipative components thoroughly, and that way it solves this heavy task. The nondissipative component , though not contributing directly to , it has an important impact to calculation via the equation , determining the most relevant parameters of the carrier system such as the density of states and the internal forces are, shared by both and . The power series expansion in terms of the scattering constant g for and the prerequisites for correct application of it are formulated.

A. Jellal
Degeneracy of the lowest landau level ans suq(2) on the Poincaré half plane
Acta Physica Slovaca 50, 253 (2000)
Abstract: It is shown that the presence of the quantum group symmetry suq(2) in the quantum Hall effect on the Poincare upper half plane governs the degeneracy of the lowest Landau level. It is also shown that the relation between the degree of degeneracy and the cyclic representation of suq(2) appears in accordance with q being a kth root of unity.

D. Ol ák, L. Šev ovi , L'. Mucha
Broad line NMR study of modified polypropylene fibres
Acta Physica Slovaca 50, 259 (2000)
Abstract: Study of drawn fibres prepared from an isostatic polypropylene modified by an ethylene aminoalkylacrylate copolymer has been done using the broad line of 1H NMR. NMR spectra were measured on the set of fibres prepared with a draw ratio from 1 to 5.5 at two temperatures, one of them corresponding to the onset of segmental motion and the other one is the minddle of the temperature interval as determined by decrease of the second moment M2. Decomposition of the spectra into elementary components related to the amorphous, intermediate and crystalline regions of partially crystalline polymers has been made. The drawing of the fibres was found to enhance the chain mobility in the amorphous region and to restrain the molecular motion in the intermediate region. Such behaviour well supports conclusions predicted in the earlier study based on the spinlattice relaxation time T1 and dynamic mechanical data treated using the WLF theory.

R. Bu ík, K. Kudela, V. Bogomolov, I.N. Myagkova, S.N. Kuznetsov, S.P. Ryumin
Distribution of gamma ray fluxes at altitude 500 km: CoronasI data
Acta Physica Slovaca 50, 267 (2000)
Abstract: Results of the statistical study of gamma ray fluxes in the energy channels 0.12  0.32 MeV, 3.0  8.3 MeV, measured by the instrument SONG on board the low altitude high inclination satellite CORONASI are presented. The geographic maps based on sets of data in March  June 1994 are constructed as well as latitudinal distribution (i.e. the variation of average fluxes with vertical cut  off rigidity) for higher energies is given. The irregular spatial structures of gamma ray flux increases in subauroral zone and at lower latitudes are discussed.
