123 research outputs found
A mathematical form of force-free magnetosphere equation around Kerr black holes and its application to Meissner effect
Based on the Lagrangian of the steady axisymmetric force-free magnetosphere
(FFM) equation around Kerr black holes(KBHs), we find that the FFM equation can
be rewritten in a new form as , where . By coordinate
transformation, the form of the above equation can be given by . Based on the form, we prove finally that the
Meissner effect is not possessed by a KBH-FFM with the condition where
and , here is the component of the vector potential ,
is the angular velocity of magnetic fields and
corresponds to twice the poloidal electric current
The no-hair theorem and black hole shadows
The successful observation of M87 supermassive black hole by the Black Hole
Event Horizon Telescope(EHT) provides a very good opportunity to study the
theory of gravity. In this work, we obtain the exact solution for the short
hair black hole (BH) in the rotation situation, and calculate in detail how
hairs affect the BH shadow. For the exact solution part, using the Newman-Janis
algorithm, we generalize the spherically symmetric short-hair black hole metric
to the rotation case (space-time lie element (2.25)). For the BH shadow part,
we study two hairy BH models. In model 1, the properties of scalar hair are
determined by the parameters and . In model 2, the scalar hair
of the BH is short hair. In this model, the shape of the BH shadow is
determined by scalar charge and . In general, various BH hairs have
different effects on the shadows, such as non-monotonic properties and
intersection phenomena mentioned in this work. Using these characteristics, it
is possible to test the no-hair theorem in future EHT observations, so as to
have a deeper understanding of the quantum effect of BHs. In future work, we
will use numerical simulations to study the effects of various hairs on BHs and
their observed properties.Comment: 19 pages, 11 figure
Destroying the Event Horizon of a Rotating Black-Bounce Black Hole
For a rotating black hole to be nonsingular, it means that there are no
spacetime singularities at its center. The destruction of the event horizon of
such a rotating black hole is not constrained by the weak cosmic censorship
conjecture, which may provide possibilities to understand the internal
structure of black hole event horizons. In this paper, we employ test particles
with large angular momentum and a scalar field with large angular momentum to
investigate the potential of destroying the event horizon of rotating
Black-Bounce black holes. Additionally, we investigate the possibility of
destroying the event horizon of a rotating Black-Bounce black hole by
considering test particles with large angular momentum and scalar fields with
large angular momentum, covering the entire range of the rotating Black-Bounce
black hole. We analyze the influence of the parameter m on the possibility of
destroying the event horizon in this spacetime. Our analysis reveals that under
extreme or near-extreme conditions, the event horizon of this spacetime can
potentially be destroyed after the absorption of particles energy and angular
momentum, as well as the scattering of scalar fields. Additionally, we find
that as the parameter m increases, the event horizon of this spacetime model
becomes more susceptible to destruction after the injection of test particles
or the scattering of scalar fields
Test the Weak Cosmic Supervision Conjecture in Dark Matter-Black Hole System
There is a possibility that the event horizon of a Kerr-like black hole with
perfect fluid dark matter (DM) can be destroyed, providing a potential
opportunity for understanding the weak cosmic censorship conjecture of black
holes. In this study, we analyze the influence of the intensity parameter of
perfect fluid DM on the destruction of the event horizon of a Kerr-like black
hole with spinning after injecting test particles and scalar fields. We find
that, when test particles are incident on the black hole, the event horizon is
destroyed by perfect fluid dark matter for extreme black holes. For nearly
extreme black holes, when the dark matter parameter satisfies i.e., the
event horizon of the black hole will not be destroyed; when the dark matter
parameter satisfies i.e., the event horizon of the black hole will
be destroyed. When a classical scalar field is incident into the black hole in
the extremal black hole case, we find that the range of mode patterns of the
scalar field that can disrupt the black hole event horizon is different for
different values of the ideal fluid dark matter intensity parameter. In the
nearly extremal black hole case, through our analysis, we have found when
and i.e., the event horizon of the
black hole can be disrupted. Our research results indicate that dark matter
might be capable of breaking the black hole horizon, thus potentially violating
the weak cosmic censorship conjecture
- …