242 research outputs found

    Two dimensional electron gas driven by strong alternating electric field

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    2D Fermi liquid driven by uniform alternating electric field at zero temperature may remain in quantum coherent non-equilibrium state. We develop a quasistatic approximation for strong and slow ac-fields and solve the problem of driven disordered 2D electron gas in high non-overlapping Landau levels. The broadening of Landau level has the Lorentz form and is inversely proportional to the amplitude of the ac-field. In the absence of electron-phonon interaction the electron distribution function is constant within the last Landau level and the diagonal dc-conductivity is zero. For weak electron-phonon interaction the dc-conductivity is anisotropic. A kinetic transition from the phonon cooling to the phonon heating is predicted.Comment: 8 pages, 1 figure REVTE

    Relativistic Heavy--Ion Collisions in the Dynamical String--Parton Model

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    We develop and extend the dynamical string parton model. This model, which is based on the salient features of QCD, uses classical Nambu-Got\=o strings with the endpoints identified as partons, an invariant string breaking model of the hadronization process, and interactions described as quark-quark interactions. In this work, the original model is extended to include a phenomenological quantization of the mass of the strings, an analytical technique for treating the incident nucleons as a distribution of string configurations determined by the experimentally measured structure function, the inclusion of the gluonic content of the nucleon through the introduction of purely gluonic strings, and the use of a hard parton-parton interaction taken from perturbative QCD combined with a phenomenological soft interaction. The limited number of parameters in the model are adjusted to e+ee^+e^- and pp --pp data. Utilizing these parameters, the first calculations of the model for pp --AA and AA--AA collisions are presented and found to be in reasonable agreement with a broad set of data.Comment: 26 pages of text with 23 Postscript figures placed in tex

    Influence of Rotation on Pulsar Radiation Characteristics

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    We present a relativistic model for pulsar radio emission by including the effect of rotation on coherent curvature radiation by bunches. We find that rotation broadens the width of leading component compared to the width of trailing component. We estimate the component widths in the average pulse profiles of about 24 pulsars, and find that 19 of them have a broader leading component. We explain this difference in the component widths by using the nested cone emission geometry. We estimate the effect of pulsar spin on the Stokes parameters, and find that the inclination between the rotation and magnetic axes can introduce an asymmetry in the circular polarization of the conal components. We analyze the single pulse polarization data of PSR B0329+54 at 606 MHz, and find that in its conal components, one sense of circular polarization dominates in the leading component while the other sense dominates in the trailing component. Our simulation shows that changing the sign of the impact parameter changes the sense of circular polarization as well as the swing of polarization angle.Comment: 20 pages, 4 Postscript figures, uses aastex.cls. Accepted for Publication in ApJ 200

    Self-Consistent Separable Rpa Approach for Skyrme Forces: Axial Nuclei

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    The self-consistent separable RPA (random phase approximation) method is formulated for Skyrme forces with pairing. The method is based on a general self-consistent procedure for factorization of the two-body interaction. It is relevant for various density- and current-dependent functionals. The contributions of the time-even and time-odd Skyrme terms as well as of the Coulomb and pairing terms to the residual interaction are taken self-consistently into account. Most of the expression have a transparent analytical form, which makes the method convenient for the treatment and analysis. The separable character of the residual interaction allows to avoid diagonalization of high-rank RPA matrices and thus to minimize the calculation effort. The previous studies have demonstrated high numerical accuracy and efficiency of the method for spherical nuclei. In this contribution, the method is specified for axial nuclei. We provide systematic and detailed presentation of formalism and discuss different aspects of the model.Comment: 42 page

    Overiew of existing solutions excitation H₀₁ wave in the circular waveguide

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    В данной работе рассмотрены осесимметричная магнитная волна H₀₁ в круглом волноводе, особенности структуры ее поля, возможности применения аномальных свойств волны H₀₁ на практике, кратко рассмотрены существующие способы возбуждения волны Н₀₁ в круглом волноводе такие как: возбуждение с помощью противофазных элементов связи, возбуждение с помощью торцевых щелей связи между прямоугольным и круглым волноводами, преобразование типов волн посредством плавных переходов между волноводами с разными типами волн, возбуждение с помощью цилиндрической щелевой антенны, возбуждение за счет подключения прямоугольного волновода узкой стенкой на закороченный торец круглого волновода. Также рассмотрены пути для получения максимального коэффициента передачи и расширения рабочей полосы устройства возбуждения.In the article axisymmetric magnetic wave H₀₁ in the circular waveguide, features of its field structure, possible implementation of its anomalous characteristics in practical systems are considered. Also existent excitation devices, such as: excitation with antiphased coupling elements, excitation with the frontal slots between rectangular and circular waveguides, modes transformation using taper between waveguides with different modes, excitation using the cylindrical slot antenna, excitation with the rectangular waveguides narrow side on the short-circuited end of the circular waveguide are described. The ways of deriving a maximal coefficient of transmission and widening of the frequency band of the excitation device are proposed

    On the nature of radio pulsars with long periods

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    It is shown that the drift waves near the light cylinder can cause the modulation of the emission with periods of the order several seconds. These periods explain the intervals between successive pulses observed in "magnetars" and radio pulsars with long periods. The model under consideration makes it possible to calculate the real rotation periods of the host neutron stars. They are less than 1 sec for the investigated objects. The magnetic fields at the surface of the neutron star of the order 10^(11)-10^(13) G and equal to the usual fields for known radio pulsarsComment: 18 pages, 4 figure

    On the connection between gamma and radio radiation spectra in pulsars

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    The model of pulsar radio emission is discussed in which a coherent radio emis-sion is excited in a vacuum gap above polar cap of neutron star. Pulsar X and gamma radiation are considered as the result of low-frequency radio emission inverse Comp-ton scattering on ultra relativistic electrons accelerated in the gap. The influence of the pulsar magnetic field on Compton scattering is taken into account. The relation of radio and gamma radiation spectra has been found in the framework of the model.Comment: 15 pages, 3 figures, Russian version accepted to JETP, partly published in JETP Letters, Vol. 85, #6 (2007

    Optimization of neuropsychological rehabilitation of higher mental functions in junior schoolchildren with mild intellectual disability

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    The article studies the effectiveness of complex neuropsychological rehabilitative impact on the nonverbal and verbal higher mental functions (HMFs) in junior schoolchildren with mild intellectual disability (ID) in comparison with the impact exclusively on the verbal HMFs in the same category of children.В статье рассматривается эффективность нейропсихологического коррекционного воздействия на невербальные и вербальные высшие психические функции детей младшего школьного возраста с легкой степенью умственной отсталости

    Review of scientific topics for Millimetron space observatory

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    This paper describes outstanding issues in astrophysics and cosmology that can be solved by astronomical observations in a broad spectral range from far infrared to millimeter wavelengths. The discussed problems related to the formation of stars and planets, galaxies and the interstellar medium, studies of black holes and the development of the cosmological model can be addressed by the planned space observatory Millimetron (the "Spectr-M" project) equipped with a cooled 10-m mirror. Millimetron can operate both as a single-dish telescope and as a part of a space-ground interferometer with very long baseline.Comment: The translation of the original article in Physics Uspekhi http://ufn.ru/ru/articles/2014/12/c

    Nuclear Scissors Mode with Pairing

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    The coupled dynamics of the scissors mode and the isovector giant quadrupole resonance are studied using a generalized Wigner function moments method taking into account pair correlations. Equations of motion for angular momentum, quadrupole moment and other relevant collective variables are derived on the basis of the time dependent Hartree-Fock-Bogoliubov equations. Analytical expressions for energy centroids and transitions probabilities are found for the harmonic oscillator model with the quadrupole-quadrupole residual interaction and monopole pairing force. Deformation dependences of energies and B(M1)B(M1) values are correctly reproduced. The inclusion of pair correlations leads to a drastic improvement in the description of qualitative and quantitative characteristics of the scissors mode.Comment: 36 pages, 5 figures, the results of calculation by another method and the section concerning currents are adde
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