Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electromagnetic field around boosted rotating black hole   The exact analytic solutions of the Maxwell equations in the exterior of a
boosted rotating black hole immersed in an external magnetic field are
obtained. The effect of boost as well as electromagnetic field on charged
particle motion and energy extraction process -- magnetic Penrose process
around black hole is studied. It justifies however the well known statement
that magnetic field greatly increases efficiency of energy extraction which is
further boosted by the boost velocity.

30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
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The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph