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;