Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The knee in the cosmic ray energy spectrum: a pulsar/supernova origin?   The origin of the prominent 'knee' in the cosmic ray energy spectrum at an
energy of several PeV is still uncertain. A recent mechanism has shown promise,
however; this involves particles from a very young pulsar interacting with the
radiation field from a very young supernova remnant. The ensuing nuclear
reaction of the particles with the photons by way of e+e- production then
causes the characteristic knee. In an earlier paper we argued that the
mechanism would imply only one source of a very rare type - if it were to
explain the spectral shape. Here we examine the mechanism in more detail and
conclude that for even a single source to work its characteristics would need
to be so unusual that the mechanism would not be possible for any known type of
pulsar-supernova combination.

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The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
20
The categories of this paper are: acc-phys