Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extracting Energy from Black Hole through Transition Region   A new scenario for extracting energy from a Kerr black hole is proposed. With
magnetic field lines connecting plasma particles inside the ergosphere with
remote loads, the frame dragging twists the field lines so that energy and
angular momentum are extracted from the plasma particles. If the magnetic field
is strong enough, the energy extracted from the particles can be so large that
the particles have negative energy as they fall into the black hole. So
effectively the energy is extracted from the black hole.
  The particles inside the ergosphere can be continuously replenished with
accretion from a disk surrounding the black hole, so a transition region with
sufficient amount of plasma is formed between the black hole's horizon and the
inner edge of the disk. Thus the energy can be continuously extracted from the
black hole through the transition region. This may be the most efficient way
for extracting energy from a Kerr black hole: in principle almost all of the
rotational energy (up to $\approx 29%$ of the total energy of the black hole)
can be extracted.

10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
2
The categories of this paper are: math
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int