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| Main Authors: | , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2509.08465 |
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| _version_ | 1866911147403247616 |
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| author | Ivashchuk, V. D. Bolokhov, S. V. Belissarova, F. B. Kydyrbay, N. Malybayev, A. N. Nurbakova, G. S. Zheng, B. |
| author_facet | Ivashchuk, V. D. Bolokhov, S. V. Belissarova, F. B. Kydyrbay, N. Malybayev, A. N. Nurbakova, G. S. Zheng, B. |
| contents | The semi-review paper studies the null geodesics which appear for black hole solutions in the gravitational $4d$ model with anisotropic fluid. The equations of state for the fluid and solutions itselves depend upon integer parameter $q = 1, 2, ...$: $p_r = -ρc^2 (2q-1)^{-1}, \quad p_t = - p_r$, where $ρ$ is the mass density, $c$ is speed of light, $p_r$ and $p_t$ are pressures in radial and transverse to radial directions, respectively. The circular null geodesics are explored and the master equation for radius $r_*$ of photon sphere is outlined as well as the proposition on existence and uniqueness of the solution to master equation obeying $r_* > r_h$, where $r_h$ is horizon radius. The relations for spectrum of quasinormal modes for a test massless scalar field in the eikonal approximation are overviewed and compared with cyclic frequencies of circular null geodesics. The shadow angles are explored. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_08465 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Photon spheres near black holes in a model with anisotropic fluid Ivashchuk, V. D. Bolokhov, S. V. Belissarova, F. B. Kydyrbay, N. Malybayev, A. N. Nurbakova, G. S. Zheng, B. General Relativity and Quantum Cosmology High Energy Physics - Theory The semi-review paper studies the null geodesics which appear for black hole solutions in the gravitational $4d$ model with anisotropic fluid. The equations of state for the fluid and solutions itselves depend upon integer parameter $q = 1, 2, ...$: $p_r = -ρc^2 (2q-1)^{-1}, \quad p_t = - p_r$, where $ρ$ is the mass density, $c$ is speed of light, $p_r$ and $p_t$ are pressures in radial and transverse to radial directions, respectively. The circular null geodesics are explored and the master equation for radius $r_*$ of photon sphere is outlined as well as the proposition on existence and uniqueness of the solution to master equation obeying $r_* > r_h$, where $r_h$ is horizon radius. The relations for spectrum of quasinormal modes for a test massless scalar field in the eikonal approximation are overviewed and compared with cyclic frequencies of circular null geodesics. The shadow angles are explored. |
| title | Photon spheres near black holes in a model with anisotropic fluid |
| topic | General Relativity and Quantum Cosmology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2509.08465 |