Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Acceleration of particles by black holes: kinematic explanation   A new simple and general explanation of the effect of acceleration of
particles by black holes to infinite energies in the centre of mass frame is
suggested. It is based on kinematics of particles moving near the horizon. This
effect arises when particles of two kinds collide near the horizon. For massive
particles, the first kind represents a particle with the generic energy and
angular momentum (I call them "usual"). Near the horizon, such a particle has a
velocity almost equal to that of light in the frame that corotates with a black
hole (the frame is static if a black hole is static). The second kind (called
"critical") consists of particles with the velocity v<c near the horizon due to
special relationship between the energy and angular momentum (or charge). As a
result, the relative velocity approaches the speed of light c, the Lorentz
factor grows unbound. This explanation applies both to generic rotating black
holes and charged ones (even for radial motion of particles). If one of
colliding particles is massless (photon), the critical particle is
distinguished by the fact that its frequency is finite near the horizon. The
existence (or absence) of the effect is determined depending on competition of
two factors - gravitational blue shift for a photon propagating towards a black
hole and the Doppler effect due to transformation from the locally nonrotating
frame to a comoving one. Classification of all possible types of collisions is
suggested depending on whether massive or massless particle is critical or
usual.

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The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin