Publication date: Jul 2018
Abstract:
The classical general relativity (GR) is remarkably confirmed in
different astronomical tests. Recently, gravitational waves have been
detected from binary black holes and binary neutron starsystems.
Moreover, constraints on alternative theories of gravity have been
obtained, so thatgraviton mass bounds have been found such as m_g <
7.7 × 10^{-23} eV. It means that theories of massive gravity,if they are
realized in nature, have to be very close to GR.In spite of a great
progress of GR now there exist a number of alternative theories of
gravity,such as f(R) theories, theories of massive gravity, scalar-
tensor theories etc.Scalar-tensor theories proposed by Hordeski are
among popular alternatives for classical general relativity (GR).There
are no-hair theorems in such a theory, however, there exist hairy black
hole solutions under some assumptions.for instantce, Babichev et al.
(2017) constructed a set of hairy static black hole solutions (for
quarticHordeski Lagrangian of scalar-tensor theory of gravity). We show
that analytical expressions for shadow sizeobtained for Reissner –
Nordström metric (with electric and tidal charges) may be usedto compare
theoretical predictions and observations for asymptotically flat black
holes with a scalar hair which mimics an electric charge.We present
analytical expressions for shadow size for static black hole solutions
with de-Sitter and anti-de-Sitter asymptotics.The relations could be
used for comparison of the theoretical models with observational data
obtained with the Event Horizon Telescope for the black hole at the
Galactic Center or in galaxy M87.
Authors:
Zakharov, Alexander; Stuchlik, Zdenek; Jaluvkova, Pavlina; Tursunov, Arman;