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    Aschenbach effect: Unexpected topology changes in the motion of particles and fluids orbiting rapidly rotating Kerr black holes

    Zdeněk Stuchlík · Leden 01, 2005 · Fyzika · 0 comments
    0

    Publication date: Jan 2005

    Abstract:
    Newtonian theory predicts that the velocity V of free test particles on
    circular orbits around a spherical gravity center is a decreasing
    function of the orbital radius r, dV/dr<0. Only very recently,
    Aschenbach [B. Aschenbach, Astronomy and Astrophysics, 425, 1075 (2004)]
    has shown that, unexpectedly, the same is not true for particles
    orbiting black holes: for Kerr black holes with the spin parameter
    a>0.9953, the velocity has a positive radial gradient for geodesic,
    stable, circular orbits in a small radial range close to the black-hole
    horizon. We show here that the Aschenbach effect occurs also for
    nongeodesic circular orbits with constant specific angular momentum
    ℓ=ℓ0=const. In Newtonian theory it is V=ℓ0/R, with
    R being the cylindrical radius. The equivelocity surfaces coincide with
    the R=const surfaces which, of course, are just coaxial cylinders. It
    was previously known that in the black-hole case this simple topology
    changes because one of the “cylinders” self-crosses. The results
    indicate that the Aschenbach effect is connected to a second topology
    change that for the ℓ=const tori occurs only for very highly spinning
    black holes, a>0.99979.

    Authors:
    Stuchlík, Zdeněk; Slaný, Petr; Török, Gabriel; Abramowicz, Marek A.;

    https://ui.adsabs.harvard.edu/abs/2005PhRvD..71b4037S

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