Quantization of triangular Lie bialgebras

We derive a universal twisting element for an arbitrary triangularγ-matrix using a simple analogue of the Fedosov quantization method. Presented at the 11th Colloquium “Quantum Groups and Integrable Systems”, Prague, 20–22 June 2002. The work of SLL is partially supported by RFBR grant 00-02-17-956 and the grant INTAS 00-262. The work of AASh is supported by RFBR grant 02-02-06879 and Russian Ministry of Education under the grant E-00-33-184. The work of VAD is partially supported by the grant INTAS 00-561 and by the Grant for Support of Scientific Schools 00-15-96557. The work of API is partially supported by the RFBR grant 00-01-00299.     

Spatiotemporal evolution of the distribution function of electrons in sign-changing electric field

A numerical model for solving the Boltzmann unsteady non-local kinetic equation for the distribution function of electrons over energy is constructed. The Boltzmann equation for isotropic part of the distribution function written in natural variables the kinetic energy — the coordinate was solved by the pseudo-unsteady method. The model was applied for describing the spatiotemporal evolution of the distribution function of electrons in a uniform electric field. For a model distribution of the electric field with the “negative” value in the Faraday dark space and the “positive” value in the positive column of the glow discharge, the main macroscopic parameters of electrons are obtained, the diffusion mechanism of the electron current transfer in the negative electric field region is confirmed. The work was financially supported by the Russian Foundation for Basic Research (Grant No. 07-02-00781-a) and by State Contract No. 02.513.11.3242.     

Many-body calculations for the relaxed (110) surface of GaAs

Quantum Monte Carlo methods are a stochastic approach to directly tackle the manybody problem in solids. They have proven to describe virutually exactly the ground state of correlated bulk systems, like the homogeneous electron gas or solids of C, Ge, Si and GaAs. Especially Variational quantum Monte Carlo calculations using nonlocal ab initio pseudopotentials offer a way to study systematically many-body effects at solid surfaces, safely founded on the variational principle “the lower the energy, the better the wave function”. Here we report on first attempts for the relaxed (110) surface of GaAs, serving as a prototype of semiconductor surfaces. A finite layer geometry is chosen as the boundary condition of the multidimensional stochastic integration scheme. The exact many-body Hamiltonian is cast in a form allowing for rapid evaluation. New parameters in the correlated trial wave function increase the variational freedom necessary to take into account the influence of the surface. Their physical meaning and their statistical significance are discussed in detail. Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999. This work was supported by the Deutsche Forschungsgemeinschaft under Grant No. Scha 360/17-1. Our calculations were performed on the Cray-T3E at the Zentralinstitut für Angewandte Mathematik, Forschungszentrum Jülich, and on the Cray-T3E at the Konrad-Zuse-Zentrum für Informationstechnik, Berlin.     

Continuity conditions for finite-dimensional representations of some locally bounded groups

Necessary and sufficient conditions are obtained for the continuity of finite-dimensional representations of “almost divisible” locally pseudocompact groups in terms of the oscillations of these representations at a point. Applications to the continuity problem for finite-dimensional representations of almost connected locally compact groups and to the theory of quasirepresentations are given. To the blessed memory of Eckehart Hotzel Partially supported by the Russian Foundation for Basic Research under grant no. 02-01-00574, by the Program of Supporting the Leading Scientific Schools under grant no. NSh 619.203.1, and by an INTAS grant.     

Poly(organylsilylene)s — perspective materials for optoelectronics

Poly(organylsilylene)s with their uninterrupted chains of silicon atoms are a new class of materials with significant delocalization of electrons along the polymer chain. Their electronic structure, optical properties, photoconductivity, electroluminescence, and photorefractivity are discussed on the model compound poly[methyl(phenyl)silylene]. Their unusual electrical and optical properties, such as high quantum generation efficiency, high charge-carrier mobility, efficient luminescence, and optical non-linearity, can be utilized in some optoelectronic devices. Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17, 1998. This work was suported by the Grant Agency of the Academy of Sciences of the Czech Republic (grant No. A1050901) and by the Grant Agency of the Czech Republic (grant No. 106/98/0700).     

Quantum relativistic Toda chain at root of unity: invariant approach

Recent results, concerning the quantum relativistic Toda chain at root of unity, are interpreted in this note from the point of view of invariant auxiliary linear problem. Such form of the linear problem arises in the three-dimensional integrable systems, and several results from the three dimensional models are applied to the relativistic Toda chain. Presented at the 10th International Colloquium on Quantum Groups: “Quantum Groups and Integrable Systems”, Prague, 21–23 June 2001. This work was supported in part by the grant INTAS OPEN 00-00055. S.P.’s work was supported by the grants RFBR 00-02-16477 and grant for support of scientific schools RFBR 00-15-96557, S.S’s work was supported by the grant RFBR 01-01-00201.     

Organic electroluminescent devices and their application

Several organic electroluminescent devices have been fabricated by multi-source high vacuum deposition system. For high brightness organic electroluminescent device, the maximum brightness is over 40000 cd/m². For quantum well structures, quantum size effect has been investigated and the high light emission efficiencies of the devices have been obtained. White-light emission from organic multi-quantum well structures is proposed at first. Brightness of the white-light MQW devices reaches 4000 cd/m² at 17 V. Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17, 1998. The research is supported by the National “863” Project of China [No. 863-307-05-05(02)] and by the National Natural Science Foundation of China [No. 69637010].     

Structural and photoluminescent properties of ZnO films deposited by radio frequency reactive sputtering

Zinc oxide films with c-axis preferred orientation were deposited on silicon (100) substrates by radio frequency (RF) reactive sputtering. The properties of the sam- ples were characterized by X-ray diffractometer, X-ray photoelectron spectroscopy and fluorescent-spectrophotometer. The effect of sputtering power and substrate temperature on the structural and photoluminescent (PL) properties of the ZnO films was investigated. The results indicated that when the sputtering power is 100 W and the substrate temperature is 300-400℃, it is suitable for the growth of high c-axis orientation and small strain ZnO films. A violet peak at about 380 nm and a blue band at about 430 nm were observed in the room temperature photolumines- cence spectra, and the origin of blue emission was investigated.     

Experimental study and mathematical modelling of heat transfer processes in heat accumulating media

Experimental results on reversing non-stationary heat transfer are presented for filtration of an air flow through an immobile heat accumulating medium consisting of lead (D = 2.0, 3.5, and 4.5 mm) and glass (D = 3.2 mm) balls. The studied device imitated the cyclic modes of heat regeneration in the ventilation system for domestic and office rooms. Dependency between the time of flow switching and Re number was measured. The mathematical model describing heat transfer between a gas flow and an immobile layer of balls was developed. Good correspondence between the experimental data and calculation results is observed for high Reynolds numbers. For low Re numbers the effect of heat losses is considerable, and experimental time of flow switching is shorter than the calculation one. The work was financially supported by the President of the Russian Federation (Grant No. NSh 6526.2006.3), Russian Foundation for Basic Research (Grant No. 06-08-00982), Foundation “Global energy” and Program “Energy saving of SB RAS”.     

Effect of free electrons on growth of “cancers” in mixed electronic-ionic conductors

The reasons for the anomalously rapid (for solids) growth of “cancers” (filamentary crystals, hills, pores, and other formations) on the surface of samples of superionic conductors with mixed electronic-ionic conductivity (of the type Cu_2−x Se and Ag₂Te) are discussed. The effects are attributed to the acceleration of mobile ions and activated ions in the “core” of the superionic by free electrons in the joint “chemical” diffusion of ions and electrons in the samples. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 2, 97–100 (25 July 1996)     

Kinetic Monte Carlo simulations of Si/Si(111)7×7 homoepitaxy

Kinetic processes that influence epitaxial growth of thin films are being more and more explored. Recent observations of growth on reconstructed surfaces suggested that material attachment to existing islands may be hindered by a barrier to attachment. We present a kinetic Monte Carlo model of Si/Si(111)7×7 homoepitaxy with the barrier to attachment implemented. We show that this model successfully reproduces available experimental results obtained during initial stages of growth and during surface relaxation. We show that the high scaling exponents experimentally observed are due to specific growth kinetics of the Si/Si(111)7×7 system. Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999. This work was supported by the Grant Agency of the Czech Republic, project GAČR 202/97/1109 and by the Volkswagen Stiftung.     

Peculiarities of the ignition of propane-air premixed flows by CO2 laser radiation

Results of an experimental study of the ignition dynamics of propane-air premixed flows under pulsed-periodic laser irradiation are reported. Ignition of homogeneous flows emanating into free atmosphere is considered. A comparative analysis of experimental and predicted delay times for the ignition for a medium at rest is given. This work was supported by the President of the Russian Federation (Grant No. NSh-8597. 2006.1), by the Russian Foundation for Basic Research (Grant No. 05-01-00560) and by the Presidium of the Russian Academy of Sciences (under the Program “Fundamental Problems in Magnetoplasma Aerodynamics”).     

Electronic structure of ultrathin Cs coatings on a Si(100)2×1 surface

The electronic structure and ionization energy of submonolayer Cs coatings on a Si(100)2×1 surface is investigated by threshold photo-emission spectroscopy. Two surface bands induced by Cs adsorption are observed, and their evolution is studied as a function of coverage. It is found that there are two “adsorption locations” for Cs atoms, where they interact with active dangling bonds at the surface. It has been determined that the Cs/Si(100)2×1 interface is semiconducting all the way down to monolayer coverage. The results show that Cs adsorption is predominantly of a covalent character. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 699–702 (10 May 1997)     

Development of laminar-separating-flow perturbations on a wavy wing

The development of velocity perturbations at laminar boundary-layer separation from a wing with wavy surface has been examined. Experiments were carried out to identify flow features displayed by the spatially periodic flow structure. An analysis of the linear stability of measured velocity profiles is performed. As a result of the analysis, the influence of surface waviness on the frequency range and growth rates of instability waves was investigated, with a good agreement between calculated and experimental data. This work was supported by the Ministry of Education and Science of the Russian Federation under the Program “Development of Higher-School Scientific Potential” for the years 2006–2008 (Projects RNP 2.1.1.471 and RNP 2.1.2.3370), and also by the Russian Foundation for Basic Research (Grant No. 07-08-00164).     

The effect of the shear flow on directional solidification of SCN-3wt% Salol alloy

The directional solidification process of SCN-3wt% Salol transparent alloy is investigated in the presence of the shear flow at the liquid-solid interface. It is found that the shear flow induces a stabilizing effect on planar interface. At higher pulling rates, oscillation of the growth pattern together with fluctuation of the growth velocity takes place. With the increase of the pulling rate, the interface growth pattern transits from “planar-cellular” oscillation to “cellular-dendritic” oscillation, and the periodicity increases. The modification of the growth pattern is due to the effect of the shear flow on solute distribution, and the time and history dependent character of interface morphology evolution also plays an important role in the formation of the oscillating growth pattern. Supported by the National Natural Science Foundation of China (Grant Nos. 50331040 and 50702046)     

Results of 2D numerical simulations of subnanosecond iodine laser interaction with an al foil target

This report presents the results of a theoretical study and 2D numerical simulations of the interaction of subnanosecond iodine laser pulses with an Al-foil target. The target and laser parameters correspond to the experimental conditions of the “PERUN” iodine laser facility (IP, Prague: pulse energy <50 J, ∼300 psec, focal spot d ∼100 μm; target: Al foil of thickness 30 μm). The simulations were made by using the two-dimensional Lagrange code “ATLANT” (FIAN-IMM, Moscow). We varied the diameter of the focal spot and studied the dependence of the plasma parameters (temperature, x-ray yield, etc.) on the laser flux density and the diameter of focal spots. The numerical results were compared with experimental data. Published as Preprint No. 38 of the Lebedev Physics Institute (FIAN), Moscow, 1993.     

The Concept of Fact in German Physics around 1900: A Comparison between Mach and Einstein

Physics in Perspective - The concept of “fact” has a history. Over the past centuries, physicists have appropriated it in various ways. In this article, we compare Ernst Mach and Albert...     

Open-system density matrix description of an STM-driven atomic switch: H on Si(100)

Previous experiments indicate that an STM (scanning tunnelling microscope) can be used to switch a hydrogen atom at a partially hydrogen-covered Si(100)-2×1 surface, from one Si atom of a Si dimer to a neighbouring, empty Si site [U.J. Quaade et al., Surf. Sci. 415, L1037, 1998]. It has been suggested that the switching occurs via a transient positive ion resonance state. In an earlier paper, we have examined the switching process for the “above threshold” regime when the bias is large enough to directly populate the positive ion resonance. In the present paper we study the “below threshold” regime instead, where the switching is more appropriately modelled as a ladder climbing over the barrier, in the ground electronic state. For this purpose we solve the Liouville–von Neumann equation in Lindblad form, describing a switching H atom on a Si dimer. STM-induced transition rates between vibrational levels are estimated from cluster calculations, assuming contributions both from a dipole and a resonance scattering mechanism. Vibrational relaxation is also included, as well as finite temperature and field effects. The switching rate in a current regime of about 1 to 10 nA scales highly non-linearly with current, and it is found to be governed by vibrational “ladder climbing” and subsequent tunnelling through the top of the ground state barrier. Multi-phonon processes also play a role. As a result of tunnelling, pronounced isotope effects are observed when replacing H with D. It is further argued that resonance-mediated inelastic scattering dominates over dipole excitation, and that the STM switch is stable also at room temperature.     

Investigation of radial profiles of vibrational and rotational temperatures in nitrogen DC glow discharge

Spatially resolved measurements of vibrational and rotational temperature determined from the N₂(C) nitrogen bands intensities have been performed by means of optical scanner of original construction. It has been found that radial variations of studied bands are independent of pressure and discharge current under our experimental conditions, i.e. in the pressure range (100–300) Pa and for discharge current up to 40 mA. Moreover, it has been found that vibrational as well as rotational temperatures stay almost constant in the radial direction. No radial changes of both temperatures can be explained by good thermal conductivity of the positive column of DC glow discharge. This research was supported by grants: Charles University No. GAUK 194/01, Ministry of Education of Czech Republic MSM 11320002, and Grant Agency of Czech Republic GAČR 202/03/0827. The theme of presented article was included in the EU project No. G1RT-CT-2002-05083 “Plasmatech”.