Precessing and periodic motions around a black-bounce/traversable wormhole
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Regular Article - Theoretical Physics
Precessing and periodic motions around a black-bounce/traversable wormhole Tian-Yi Zhou1,2 , Yi Xie1,2,a 1 2
School of Astronomy and Space Science, Nanjing University, Nanjing 210023, China Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Ministry of Education, Nanjing 210023, China
Received: 1 October 2020 / Accepted: 11 November 2020 © The Author(s) 2020
Abstract We investigate precessing and periodic geodesic motions of timelike particles around a black-bounce/traversable wormhole. After obtaining its semi-classic and relativistic periastron advance, we find a preliminary bound on the scale length of such a spactime based on the detected precession of the star S2 around the Galactic Center. We also study periodic orbits around it and find that the variation of the scale length can change the taxonomy of the periodic orbits and cause the transition from a periodic orbit to a quasi-periodic one and vice versa.
1 Introduction Observations through gravitational waves [1–6] and radio waves [7–12] have shown that black holes are widespread in the Universe. As the simplest celestial object predicted by Einstein’s general relativity (GR), a black hole has some distinguishing features, such as the event horizon and the central singularity, whereas these two characteristics bring serious problems as well, like the loss of information and breakdown of GR. Proposals to remove the singularity cover construction of a regular core [13–16], bounce by the quantum pressure [17–19] and formation of a quasi-black hole [20–23] (see Ref. [24] for a review). Recently, a black-bounce/traversable wormhole spacetime has arisen [25] and it can interpolate between a regular black hole (a black bounce) and a traversable wormhole, reducing to the Ellis wormhole [26] in the massless case. Because of its interesting characters, a lot of attention has been paid on it. A time-dependent version [27] of such a spacetime was extended from its original static one and a spherically symmetric thin-shell traversable wormhole was established by it [28]. Its quasinormal modes [29], absorpa e-mail:
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tion of scalar waves [30] and gravitational lensing [31] were also investigated. In the present work, we will focus on the bound geodesic orbits of timelike particles around the black-bounce/traversable wormhole, which were absent in the literature. Bound orbits can be further classified into precessing and periodic orbits. It is no doubt that the anomalous perihelion advance of Mercury belongs to the earliest observational evidences of GR [32] and its next-to-leading-order advance has been examined as well [33–35]. Nowadays, the periastron advances of the planets around the Sun [36–43] and other stars [44–47], of binary stars [48–54] and of stars around the supermassive black hole in the Galactic Center Sgr A* [55–64] have been widely adopted and discussed for probing and constraining modified theories of gravity and new physics.
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