Regular Article - Theoretical Physics
The existence of null circular geodesics outside extremal spherically symmetric asymptotically flat hairy black holes
School of Mathematical Sciences, Qufu Normal University, 273165, Qufu, Shandong, China
Accepted: 30 March 2023
Published online: 27 April 2023
The existence of null circular geodesics in the background of non-extremal spherically symmetric asymptotically flat black holes has been proved in previous works. An interesting question that remains, however, is whether extremal black holes possess null circular geodesics outside horizons. In the present paper, we focus on the extremal spherically symmetric asymptotically flat hairy black holes. We show the existence of the fastest circular trajectory around an extremal black hole. As the fastest trajectory corresponds to the position of null circular geodesics, we prove that null circular geodesics exist outside extremal spherically symmetric asymptotically flat hairy black holes.
© The Author(s) 2023
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