Non-monotonic Keplerian velocity profiles around near-extreme braneworld Kerr black holes

Abstract\nWe study the non-monotonic Keplerian velocity profiles related to locally non-rotating frames (LNRF) in the field of near-extreme braneworld Kerr black holes and naked singularities in which the non-local gravitational effects of the bulk are represented by a braneworld tidal charge b and the 4D geometry of the spacetime structure is governed by the Kerr?Newman geometry. We show that positive tidal charge has a tendency to restrict the values of the black hole dimensionless spin a admitting existence of the non-monotonic Keplerian LNRFvelocity profiles ; the non-monotonic profiles exist in the black hole spacetimes with tidal charge smaller than b = 0.41005 (and spin larger than a = 0.76808). With decreasing value of the tidal charge (which need not be only positive), both the region of spin allowing the non-monotonicity in the LNRF-velocity profile around braneworld Kerr black hole and the velocity difference in the minimummaximum parts of the velocity profile increase implying growing astrophysical relevance of this phenomenon.

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