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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  • Некоторые метрики заблокированы вашими 
    Тип записи:Публикация,
    Thin accretion-disc transfer functions in the q-metric spacetime: quadrupolar lensing signatures
    (Cornell University, 2026-09-07) ; ;
    Aray Muratkhan
    ;
    ;
    Aliya Taukenova
    We study geometrically thin equatorial disc images in the static, axisymmetric q-metric spacetime using backward ray tracing. The Schwarzschild solution is recovered at $q=0$; for the nonzero deformations considered here, $r=2M$ is a curvature singularity rather than an event horizon. For a distant nearly face-on observer, we construct the first three equatorial transfer functions $r_m(b;q)$. In the {Schwarzschild} limit, the resolved third-crossing interval contains the critical impact parameter $b=3\sqrt{3}M$. As $q$ increases from $-0.3$ to $0.3$, the branch center shifts from $b_{3,c}/M\simeq3.716$ to $6.702$. In units of the physical monopole mass $\mathcal M=(1+q)M$, it instead decreases from $b_{3,c}/\mathcal M\simeq5.309$ to $5.156$. Much of the displacement in metric-parameter units therefore reflects the changing monopole scale. At fixed $\mathcal M$, the inclined first-intersection maps show that the contour dimensions increase with $q$, with larger relative changes near the inner disc. A prescribed power-law emissivity and relativistic frequency-shift weighting yield direct images whose integrated flux differs from the Schwarzschild value by at most $2.4\%$. Between the endpoint models, the horizontal median-flux position increases by $8.8\%$ and the interquartile width by $14.5\%$. Within this emission prescription, the residual deformation dependence appears mainly as a displacement and broadening of the brightness distribution. Higher-order radiative contributions are not included.
  • Некоторые метрики заблокированы вашими 
    Тип записи:Публикация,
    Gravitational field of slightly deformed naked singularities
    (Springer Science+Business Media, 2022-04-01) ;
    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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    Тип записи:Публикация,
    Gravitational Refraction of Compact Objects with Quadrupoles
    (Multidisciplinary Digital Publishing Institute, 2023-02-28)
    Nurzada Beissen
    ;
    Daniya Utepova
    ;
    Medeu Abishev
    ;
    Hernando Quevedo
    ;
    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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    Тип записи:Публикация,
    Adiabatic theory in Kerr spacetimes
    (Springer Science+Business Media, 2024-05-01)
    Kuantay Boshkayev
    ;
    Gulmira Nurbakyt
    ;
    Hernando Quevedo
    ;
    Gulnara Suliyeva
    ;
    Abylaikhan Tlemissov
    Цитирования (OpenAlex) 3Цитирования (OpenCitations) 3
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    Тип записи:Публикация,
    Gravitational capture cross-section in Zipoy-Voorhees spacetimes
    (Springer Science+Business Media, 2025-05-28)
    S.B. Momynov
    ;
    Kuantay Boshkayev
    ;
    Hernando Quevedo
    ;
    Farida Belissarova
    ;
    Цитирования (OpenAlex) 5Цитирования (OpenCitations) 4
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    Тип записи:Публикация,
    Geometric properties versus particle motion in the Fan-Wang spacetime
    (Elsevier BV, 2025-06-24)
    Gulnara Suliyeva
    ;
    Kuantay Boshkayev
    ;
    Talgar Konysbayev
    ;
    Yergali Kurmanov
    ;
    Orlando Luongo
    Цитирования (OpenAlex) 6Цитирования (OpenCitations) 4