Қазақ ұлттық қыздар педагогикалық университеті / Казахский национальный женский педагогический университет

Постоянный URI для этого сообществаhttps://cris.qyzpu.edu.kz/handle/123456789/1

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2022 - 20245

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Автор: search.filters.author.Medeu Abishev

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    Gravitational field of slightly deformed naked singularities
    (Springer Science+Business Media, 2022-04-01)
    Saken Toktarbay
    ;
    Hernando Quevedo
    ;
    Medeu Abishev
    ;
    Aray Muratkhan
    Abstract We derive a particular approximate solution of Einstein equations, describing the gravitational field of a mass distribution that slightly deviates from spherical symmetry. The deviation is described by means of a quadrupole parameter that is responsible for the appearance of a curvature singularity, which is not covered by a horizon. We investigate the motion of test particles in the gravitational field of this naked singularity and show that the quadrupole parameter affects the properties of Schwarzschild trajectories. By investigating radial geodesics, we find that no effects of repulsive gravity are present. We interpreted this result as indicating that repulsive gravity is non-linear effect.
    Цитирования (OpenAlex) 12Цитирования (OpenCitations) 9
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    Gravitational Refraction of Compact Objects with Quadrupoles
    (Multidisciplinary Digital Publishing Institute, 2023-02-28)
    Nurzada Beissen
    ;
    Daniya Utepova
    ;
    Medeu Abishev
    ;
    Hernando Quevedo
    ;
    Manas Khassanov
    We use the material medium approach to derive the refractive index that can be associated with the gravitational field of a compact object with a quadrupole moment. We consider both a static deformation and a stationary rotation of the gravitational source as the source of the quadrupole. We show that up to the first order in the quadrupole, the refractive indices of both configurations are equivalent such that from the point of view of refraction, a mimicking effect can occur. This also holds at the level of the deflection angle. We argue that it is possible to use the refractive indices and the parameters of the trajectories of light rays that propagate in a gravitational field to determine the physical parameters of the source.
    Цитирования (OpenAlex) 10Цитирования (OpenCitations) 5
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    Stability Properties of Geometrothermodynamic Cosmological Models
    (Multidisciplinary Digital Publishing Institute, 2023-09-28)
    Nurzada Beissen
    ;
    Medeu Abishev
    ;
    Manas Khassanov
    ;
    Temirbolat Aitassov
    ;
    Sagira Mamatova
    We consider a particular isotropic and homogeneous cosmological model, in which the equation of state is obtained from a thermodynamic fundamental equation by using the formalism of geometrothermodynamics (GTD). The model depends effectively on three arbitrary constants, which can be fixed to reproduce the main aspects of the inflationary era and the ΛCDM paradigm. We use GTD to analyze the geometric properties of the corresponding equilibrium space and to derive the stability properties and phase transition structure of the cosmological model.
    Цитирования (OpenAlex) 1Цитирования (OpenCitations) 1
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    Nonlinear electrodynamical lensing of electromagnetic waves on the dipole magnetic field of the magnetar
    (World Scientific, 2023-12-01)
    Nurzada Beissen
    ;
    Medeu Abishev
    ;
    Saken Toktarbay
    ;
    Tursynbek Yernazarov
    ;
    Y. Aimuratov
    We study numerically a combined gravitational and nonlinear magnetic lensing effect on electromagnetic flux. A magnetar with a dipole magnetic field and background gravitational field is considered to deflect the light rays which passed through its magnetosphere. We assume a square wave front with sides [Formula: see text][Formula: see text]m as a grid with the [Formula: see text][Formula: see text]m dynamic step. At the nodes of this grid, the rays enter perpendicularly into the cubic area, which covers the main magnetic lensing region with a magnetar at the center. On the basis of general relativity (GR) and nonlinear vacuum electrodynamics, the distribution of rays by the deflection angle in the combined field of the magnetar was obtained. On the basis of the analysis of the obtained data, it is possible to assert that the magnetic field distorts the result of gravitational lensing. Therefore, the magnetar is regarded as a gravitational-magnetic lensing object, wherein the magnetic field induces axial distortion within [Formula: see text]. These results are expected to be detectable by modern instruments.
    Цитирования (OpenAlex) 5Цитирования (OpenCitations) 3
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    An overview of light ray deflection calculation by magnetars in nonlinear electrodynamics
    (2024-06-24)
    Nurzada Beissen
    ;
    Medeu Abishev
    ;
    Saken Toktarbay
    ;
    Tursynbek Yernazarov
    ;
    Manas Khassanov
    Due to the lack of experimental confirmation of the effects of nonlinear electrodynamics (NED) of vacuum on the electromagnetic wave, it remains the most pressing issue. One of the most optimal media for studying these effects, occurring in astrophysics, are magnetars. Various methods of studying the bending of a wave passing through the magnetospheres of magnetars play a key role in a deeper understanding of vacuum NED. This article reviews modern methods for determining the angle of bending of the electromagnetic wave under the effect of NED of vacuum and gravity, with special attention paid to NED of vacuum in intense electromagnetic fields, which is a characteristic feature of magnetars. The article discusses various methods and techniques used to measure these angles, as well as their potential astrophysical applications.
    Цитирования (OpenAlex) 2