Publication date: Jul 2014
Abstract:
We discuss photon and test-particle orbits in the Kehagias-Sfetsos (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 Kerr-metric solutions. The properties of the
corresponding circular orbits are qualitatively similar to those of the
Reissner-Nordström naked singularities. When event horizons are present,
the orbits outside the Kehagias-Sfetsos black hole are qualitatively
similar to those of the Schwarzschild metric.
Authors:
Vieira, Ronaldo S. S.; Schee, Jan; Kluźniak, Włodek; Stuchlík, Zdeněk; Abramowicz, Marek;