1,237 research outputs found
Equatorial circular motion in Kerr spacetime
We analyze the properties of circular orbits of test particles on the
equatorial plane of a rotating central mass whose gravitational field is
described by the Kerr spacetime. For rotating black holes and naked
singularities we explore all the spatial regions where circular orbits can
exist and analyze the behavior of the energy and the angular momentum of the
corresponding test particles. In particular, we find all the radii at which a
test particle can have zero angular momentum due to the repulsive gravity
effects generated by naked singularities. We classify all the stability zones
of circular orbits. It is shown that the geometric structure of the stability
zones of black holes is completely different from that of naked singularities.Comment: 48 pages, 40 figures, 3 Tables. To be published PRD. This work
follows the paper Phys. Rev. D Vol.83, No.2 with DOI:
10.1103/PhysRevD.83.024021 (arXiv:1012.5411v1 [astro-ph.HE]) and paper
arXiv:1103.1807v3 to be published in PR
Perfect fluid tori orbiting Kehagias-Sfetsos naked singularities
We construct perfect fluid tori in the field of the Kehagias-Sfetsos (K-S)
naked singularity representing spherically symmetric vacuum solution of the
modified Ho\v{r}ava quantum gravity that is characterized by a dimensionless
parameter , combining the gravitational mass parameter of the
spacetime with the Ho\v{r}ava parameter reflecting the role of the
quantum corrections. In dependence on the value of , the K-S naked
singularities demonstrate a variety of qualitatively different behavior of
their circular geodesics that is fully reflected in the properties of the
toroidal structures. In all of the K-S naked singularity spacetimes the tori
are located above an "antigravity" sphere where matter can stay in stable
equilibrium position, that is relevant for the stability of the orbiting fluid
toroidal accretion structures.Comment: 44 pages, 27 figures multi panel
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