2,180 research outputs found
Remarks on non-singular black holes
We briefly discuss non-singular black hole models, with the main focus on the
properties of non-singular evaporating black holes. Such black holes possess an
apparent horizon, however the event horizon may be absent. In such a case, the
information from the black hole interior may reach the external observer after
the complete evaporation of the black hole. This model might be used for the
resolution of the information loss puzzle. However, as we demonstrate, in a
general case the quantum radiation emitted from the black hole interior,
calculated in the given black hole background, is very large. This outburst of
the radiation is exponentially large for models with the redshift function
. We show that it can be suppressed by including a non-trivial
redshift function. However, even this suppression is not enough to guarantee
self-consistency of the model. This problem is a manifestation of a general
problem, known as the "mass inflation". We briefly comment on possible ways to
overcome this problem in the models of non-singular evaporating black holes.Comment: 10 pages, Extended version of the plenary talk given at a Joint
Meeting: 13th International Conference on Gravitation, Astrophysics, and
Cosmology 15th Italian-Korean Symposium on Relativistic Astrophysics, Seoul,
July 03--07, 201
Information loss problem and a `black hole' model with a closed apparent horizon
In a classical description the spacetime curvature inside a black hole
infinitely grows. In the domain where it reaches the Planckian value and
exceeds it the Einstein equations should be modified. In the absence of
reliable theory of quantum gravity it is instructive to consider simplified
models. We assume that a spacetime curvature is limited by some value (of the
order of the Planckian one). We use modified Vaidya metric, proposed by
Hayward, to describe the black hole evaporation process. In such a spacetime
the curvature near remains finite, it does not have an event horizon and
its apparent horizon is closed. If the initial mass of such a `black hole' is
much larger than the Planckian one its properties (as seen by an external
observer) are practically the same as properties of the `standard' black hole
with the event horizon. We study outgoing null rays in the vicinity of the
outer apparent and introduce a notion of quasi-horizon. We demonstrate that
particles, trapped inside a `black hole' during the evaporation process,
finally may return to external space after the evaporation is completed. We
also demonstrate that such quanta would have very large blue-shift. The absence
of the event horizon makes it possible restoration of the unitarity in
evaporating black holes.Comment: 18 pages, 6 figures. New references added with their brief
discussion. Conformal Carter-Penrose diagram is added. Found misprints are
correcte
Classical self-energy and anomaly
We study the problem of self-energy of pointlike charges in higher
dimensional static spacetimes. Their energy, as a functional of the spacetime
metric, is invariant under a specific continuous transformation of the metric.
We show that the procedure of regularization of this formally divergent
functional breaks this symmetry and results in an anomalous contribution to the
finite renormalized self-energy. We proposed a method of calculation of this
anomaly and presented an explicit expressions for it in the case of a scalar
charge in four and five-dimensional static spacetimes. This anomalous
correction proves to be zero in even dimensions, but it does not vanish in
odd-dimensional spacetimes.Comment: 5 page
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