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Hole System (hole + system)

Distribution by Scientific Domains
Physics and Astronomy91%
Distribution within Physics and Astronomy
Solid State Physics54%
Astronomy & Astrophysics45%

Kinds of Hole System

  • black hole system
    		•

    Selected Abstracts

    General Relativity effects and line emission

    ASTRONOMISCHE NACHRICHTEN, Issue 10 2006
    G. Matt
    Abstract General Relativity effects (gravitational redshift, light bending, ,) strongly modify the characteristics of the lines emitted close to the Black Hole in Active Galactic Nuclei and Galactic Black Hole systems. These effects are reviewed and illustrated, with particular emphasis on line emission from the accretion disc. Methods, based on the iron line, to measure the two astrophysically relevant parameters of a Black Hole, the mass and spin, are briefly discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Chandra monitoring observations of the ultraluminous X-ray source NGC 5204 X-1

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
    T. P. Roberts
    ABSTRACT We report the results of a two-month campaign conducted with the Chandra X-ray observatory to monitor the ultraluminous X-ray source (ULX) NGC 5204 X-1. This was composed of a 50-ks observation, followed by ten 5-ks follow-ups spaced initially at ,3, then at ,10-d intervals. The ULX flux is seen to vary by factors ,5 on time-scales of a few days, but no strong variability is seen on time-scales shorter than an hour. There is no evidence for a periodic signal in the X-ray data. An examination of the X-ray colour variations over the period of the campaign shows the ULX emission consistently becomes spectrally harder as its flux increases. The X-ray spectrum from the 50-ks observation can be fitted by a number of disparate spectral models, all of which describe a smooth continuum with, unusually for a ULX, a broad emission feature evident at 0.96 keV. The spectral variations, both within the 50-ks observation and over the course of the whole campaign, can then be explained solely by variations in the continuum component. In the context of an optically thick corona model (as found in other recent results for ULXs) the spectral variations can be explained by the heating of the corona as the luminosity of the ULX increases, consistent with the behaviour of at least one Galactic black hole system in the strongly Comptonized very high state. We find no new evidence supporting the presence of an intermediate-mass black hole in this ULX. [source]

    Computational methods for studies of multiexciton complexes,

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2006
    T. Vänskä
    Abstract Powerful computational methods are presented for studies of energy levels, photon-recombination rates, and phonon-relaxation rates of neutral and charged multiexciton complexes at correlated levels of theory. The electron,hole system is described by a two-band effective-mass Hamiltonian. The one-particle functions are expanded in a basis set consisting of anisotropic Gaussian functions. The many-body Hamiltonian constructed in the space of the antisymmetric products of one-particle functions is diagonalized using general coupled-cluster and configuration-interaction methods. The expansion coefficients of the coupled-cluster and configuration-interaction wave functions are obtained by solving the corresponding equations using direct iterative algorithms. We demonstrate the potential of the computational approaches by calculating total energies of multiexciton complexes at coupled-cluster and configuration-interaction levels. Computational methods for studies of radiative recombination and phonon-relaxation rates have also been developed and results are reported for radiative recombination rates and recombination energies of the exciton, biexciton, and of the positive and the negative trions confined in a InGaAs/GaAs quantum-dot sample. Phonon-relaxation rates have been calculated for a few low-lying ,g states of the exciton complex of the same quantum-dot sample. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Diamagnetic and nonlinear Zeeman shifts in spatially separated electron and hole layers of semiconductor heterostructures with disorder

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003
    J. Desforges
    Abstract The effect of the diamagnetic shift on the formation of excitons is investigated for double layer semiconductor systems in which electrons and holes are spatially separated. The effect of disorder due to interface roughness of the double layer structures is included in the calculation of exciton density. Numerical calculations are performed based on an effective lattice-gas model where the electron,hole system is divided into unit cells. The exciton density is calculated by using the partition function method. The effect of the nonlinear Zeeman splitting is also included in the numerical calculations. It is found that the density of the optically allowed exciton states (excitons with Sz = 0) increases under the influence of either or both the diamagnetic and the nonlinear Zeeman shifts. [source]

    Metastable spin configuration of two-dimensional hole system in the quantum Hall regime

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2006
    Katsuyoshi Kodera
    Abstract We have observed hysteretic behavior of magnetoresistance with slow dynamics in a GaAs/AlGaAs two-dimensional hole system (2DHS) in quantum Hall regime. The relaxation towards the stable state exhibits a distinct change in behaviour between the filling ranges , > 1 and , < 1, suggesting a spin-related mechanism. The relaxation time scale on the order of an hour was observed at the lowest temperature. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Untersuchungen hinsichtlich der Dauerhaftigkeit von Wärmedämmverbundsystemen (WDVS) mit Holzfaserdämmplatten

    BAUPHYSIK, Issue 4 2009
    Norbert Rüther Dipl.
    Wärme; Versuche; thermal insulation and heat; experimental set-up Abstract Der Schutz der Dämmstoffe von WDVS vor Umwelteinflüssen wird hauptsächlich durch das Putzssystem sichergestellt. Haftet dieses nicht mehr am Dämmstoff, so sind umfangreiche Sanierungsmaßnahmen erforderlich. Mit Hilfe von Haftzugprüfungen aus künstlich gealterten Proben sollten Prognosen über die Dauerhaftigkeit unter realen Bedingungen abgeleitet werden. Es wurde festgestellt, dass die Festigkeit von Platten mit hoher Anfangsfestigkeit über die Zeit um etwa 25 % geringer wird, dann jedoch auf dem Festigkeitsniveau verbleibt. Bei Platten mit niedriger Anfangsfestigkeit wurde kein relevanter Festigkeitsabfall ermittelt. Experimental analysis of the durability of external thermal insulation compound systems (ETICS) using wood fibre insulating boards. The insulation of external thermal insulation compound systems has to be protected by the rendering system. The failure of the rendering system, e.g. due to the loss of bonding strength to the insulation can lead to a failure of the hole system. Forecasts of the durability should be done by using test results of tensile bond strength from samples which were stressed by artificial weathering. Boards with a relatively high strength lose nearly 25 % of their strength and continue in a while at that level. Boards with a relatively low strength do not lose there strength any more. [source]

    X-ray reflection in accreting stellar-mass black hole systems

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007
    R. R. Ross
    ABSTRACT The X-ray spectra of accreting stellar-mass black hole systems exhibit spectral features due to reflection, especially broad iron K, emission lines. We investigate the reflection by the accretion disc that can be expected in the high/soft state of such a system. First, we perform a self-consistent calculation of the reflection that results from illumination of a hot, inner portion of the disc with its atmosphere in hydrostatic equilibrium. Then, we present reflection spectra for a range of illumination strengths and disc temperatures under the assumption of a constant-density atmosphere. Reflection by a hot accretion disc differs in important ways from that of a much cooler disc, such as that expected in an active galactic nucleus. [source]

    Iron K, line profiles and the inner boundary condition of accretion flows

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2003
    A. Merloni
    ABSTRACT Recent X-ray observations have shown evidence for exceptionally broad and skewed iron K, emission lines from several accreting black hole systems. The lines are assumed to be due to fluorescence of the accretion disc illuminated by a surrounding corona and require a steep emissivity profile increasing into the innermost radius. This appears to question both standard accretion disc theory and the zero-torque assumption for the inner boundary condition, both of which predict a much less extreme profile. Instead it argues that a torque may be present due to magnetic coupling with matter in the plunging region or even to the spinning black hole itself. Discussion so far has centred on the torque acting on the disc. However, the crucial determinant of the iron line profile is the radial variation of the power radiated in the corona. Here we study the effects of different inner boundary conditions on the coronal emissivity and on the profiles of the observable Fe K, lines. We argue that in the extreme case where a prominent highly redshifted component of the iron line is detected, requiring a steep emissivity profile in the innermost part and a flatter one outside, energy from the gas plunging into the black hole is being fed directly to the corona. [source]

    Interaction effects in high-mobility two-dimensional electron and hole systems

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2005
    A. K. Savchenko
    Abstract Electron,electron interaction in the presence of impurities is studied in two-dimensional systems where the parameter kBT,/, changes from 0.1 to 10 (, is the momentum relaxation time). This corresponds to the intermediate and ballistic regimes of electron interaction. We analyse the interaction correction to the Drude conductivity in terms of recent theories and show that it is strongly dependent on the character of the impurity potential. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Interwell exciton dispersion engineering, coherent phonons generation and optical detectionof exciton condensate

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2004
    Yu. E. Lozovik
    This issue's Editor's Choice [1] discusses interwell excitons in coupled quantum wells as a candidate for observation of different phases in an exciton system, including the very interesting phenomenon of Bose condensation. The cover picture shows schematically how the generation of coherent phonons and the angular distribution of the exciton photoluminescence (PL) from the quantum well system can be controlled by the external electric and magnetic fields. The first author, Yurii E. Lozovik, is head of the Laboratory of Spectroscopy of Nanostructures at the Institute of Spectroscopy and also Professor of Physics at the Moscow Physical and Technical Institute. His main interests are electron and electron,hole systems in nanostructures, cluster physics, quantum electrodynamics in a cavity, matter in strong magnetic fields, nanotechnology, ultrafast and near field optics, and computer simulations. [source]