Regular Article - Theoretical Physics
Do the Einstein-matter field equations always predict the existence of light rings in black-hole spacetimes?
The Ruppin Academic Center, 40250, Emeq Hefer, Israel
2 The Hadassah Academic College, 91010, Jerusalem, Israel
Accepted: 24 July 2022
Published online: 2 August 2022
We are used to think of null circular geodesics as an integral part of black-hole spacetimes. In the present compact paper we reveal the physically interesting fact that, contrary to the general belief, the non-linearly coupled Einstein-matter field equations do not a priori guarantee the existence of external light rings in extremal black-hole spacetimes. This observation raises the intriguing possibility of having extremal black-hole spacetimes that possess no external light rings. We prove that these unique black holes, if exist, are characterized by non-positive tangential pressures on their surfaces.
© The Author(s) 2022
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