Circular geodesics of naked singularities in the KehagiasSfetsos metric of Hořava's gravity
Abstract
We discuss photon and testparticle orbits in the KehagiasSfetsos (KS) metric of Hořava's gravity. For any value of the Hořava parameter ω, there are values of the gravitational mass M for which the metric describes a naked singularity, and this is always accompanied by a vacuum "antigravity sphere" on whose surface a test particle can remain at rest (in a zero angular momentum geodesic), and inside which no circular geodesics exist. The observational appearance of an accreting KS naked singularity in a binary system would be that of a quasistatic spherical fluid shell surrounded by an accretion disk, whose properties depend on the value of M, but are always very different from accretion disks familiar from the Kerrmetric solutions. The properties of the corresponding circular orbits are qualitatively similar to those of the ReissnerNordström naked singularities. When event horizons are present, the orbits outside the KehagiasSfetsos black hole are qualitatively similar to those of the Schwarzschild metric.
 Publication:

Physical Review D
 Pub Date:
 July 2014
 DOI:
 10.1103/PhysRevD.90.024035
 arXiv:
 arXiv:1311.5820
 Bibcode:
 2014PhRvD..90b4035V
 Keywords:

 04.50.Kd;
 04.70.Bw;
 04.40.Dg;
 95.10.Eg;
 Modified theories of gravity;
 Classical black holes;
 Relativistic stars: structure stability and oscillations;
 Orbit determination and improvement;
 General Relativity and Quantum Cosmology;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 8 pages, 9 figures