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| Main Authors: | , , , , |
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| Format: | Preprint |
| Published: |
2023
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2305.11208 |
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| _version_ | 1866910503072169984 |
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| author | Amo, Masaya Izumi, Keisuke Yoshino, Hirotaka Tomikawa, Yoshimune Shiromizu, Tetsuya |
| author_facet | Amo, Masaya Izumi, Keisuke Yoshino, Hirotaka Tomikawa, Yoshimune Shiromizu, Tetsuya |
| contents | In asymptotically flat spacetimes, bearing the null geodesics reaching the future null infinity in mind, we propose new concepts, the "dark horizons" as generalizations of the photon sphere. They are defined in terms of the structure of escape/capture cones of photons with respect to a unit timelike vector field. More specifically, considering a two-sphere that represents a set of emission directions of photons, the dark horizons are located at positions where a hemisphere is marginally included in the capture and escape cones, respectively. We show that both of them are absent in the Minkowski spacetime, while they exist in spacetimes with black hole(s) under a certain condition. We derive the general properties of the dark horizons in spherically symmetric spacetimes and explicitly calculate the locations of the dark horizons in the Vaidya spacetime and the Kerr spacetime. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2305_11208 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | A generalization of photon sphere based on escape/capture cone Amo, Masaya Izumi, Keisuke Yoshino, Hirotaka Tomikawa, Yoshimune Shiromizu, Tetsuya General Relativity and Quantum Cosmology High Energy Astrophysical Phenomena High Energy Physics - Theory In asymptotically flat spacetimes, bearing the null geodesics reaching the future null infinity in mind, we propose new concepts, the "dark horizons" as generalizations of the photon sphere. They are defined in terms of the structure of escape/capture cones of photons with respect to a unit timelike vector field. More specifically, considering a two-sphere that represents a set of emission directions of photons, the dark horizons are located at positions where a hemisphere is marginally included in the capture and escape cones, respectively. We show that both of them are absent in the Minkowski spacetime, while they exist in spacetimes with black hole(s) under a certain condition. We derive the general properties of the dark horizons in spherically symmetric spacetimes and explicitly calculate the locations of the dark horizons in the Vaidya spacetime and the Kerr spacetime. |
| title | A generalization of photon sphere based on escape/capture cone |
| topic | General Relativity and Quantum Cosmology High Energy Astrophysical Phenomena High Energy Physics - Theory |
| url | https://arxiv.org/abs/2305.11208 |