181 research outputs found
New Gauss-Bonnet black holes with curvature induced scalarization in the extended scalar-tensor theories
In the present paper we consider a class of extended
scalar-tensor-Gauss-Bonnet (ESTGB) theories for which the scalar degree of
freedom is excited only in the extreme curvature regime. We show that in the
mentioned class of ESTGB theories there exist new black hole solutions which
are formed by spontaneous scalarization of the Schwarzaschild balck holes in
the extreme curvature regime. In this regime, below certain mass, the
Schwarzschild solution becomes unstable and new branch of solutions with
nontrivial scalar field bifurcate from the Schwarzschild one. As a matter of
fact, more than one branches with nontrivial scalar field can bifurcate at
different masses but only the first one is supposed to be stable. This effect
is quite similar to the spontaneous scalarization of neutron stars. In contrast
with the standard spontaneous scalarization of neutron stars which is induced
by the presence of matter, in our case the scalarization is induced by the
curvature of the spacetime.Comment: 13 pages, 7 figure
Black hole no-hair theorem for self-gravitating time-dependent spherically symmetric multiple scalar fields
We prove under certain weak assumptions a black hole no-hair theorem in
spherically symmetric spacetimes for self-gravitating time-dependent multiple
scalar fields with an arbitrary target space admitting a Killing field with a
non-empty axis and arbitrary non-negative potential invariant under the flow of
the Killing field. It is shown that for such configurations the only
spherically symmetric and asymptotically flat black hole solutions consist of
the Schwarzschild metric and a constant multi-scalar map. In due course of the
proof we also unveil the intrinsic connection of the time-dependence of the
scalar fields with the symmetries of the target space.Comment: 6 page
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