Photon Spheres near Black Holes in a Model with an Anisotropic Fluid
Ivashchuk V.D. Bolokhov S.V. Belissarova F.B. Kydyrbay N. Malybayev A.N. Nurbakova G.S. Zheng B.
September 2025Pleiades Publishing
Gravitation and Cosmology
2025#31Issue 3392 - 400 pp.
Abstract: This semi-review paper studies null geodesics which exist for black hole solutions in a gravitational 4D model with an anisotropic fluid. The equations of state for the fluid and the solutions depends on the integer parameter :, where is the mass density, is the speed of light, and are pressures in the radial and transverse directions, respectively. Circular null geodesics are explored, and a master equation for the radius of a photon sphere is found, as well as the proposition on the existence and uniqueness of a solution to the master equation, obeying, where is the horizon radius. Relations for the spectrum of quasinormal modes for a test massless scalar field in the eikonal approximation are overviewed and compared with the cyclic frequencies of circular null geo desics. Shadow angles are explored.
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Peoples’ Friendship University of Russia (RUDN University), Moscow, 117198, Russian Federation
Research Center for Applied Metrology—Rostest, Moscow, 119361, Russian Federation
Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
Peoples’ Friendship University of Russia (RUDN University)
Research Center for Applied Metrology—Rostest
Al-Farabi Kazakh National University
10 лет помогаем публиковать статьи Международный издатель
Книга Публикация научной статьи Волощук 2026 Book Publication of a scientific article 2026