Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Origin of the light cosmic ray component below the ankle   The origin and nature of the ultrahigh energy cosmic rays remains a mystery.
However, considerable progress has been achieved in past years due to
observations performed by the Pierre Auger Observatory and Telescope Array.
Above $10^{18}$ eV the observed energy spectrum presents two features: a
hardening of the slope at $\sim 10^{18.6}$ eV, which is known as the ankle, and
a suppression at $\sim 10^{19.6}$ eV. The composition inferred from the
experimental data, interpreted by using the current high energy hadronic
interaction models, seems to be light below the ankle, showing a trend to
heavier nuclei for increasing values of the primary energy. Also, the
anisotropy information is consistent with an extragalactic origin of this light
component that would dominate the spectrum below the ankle. Therefore, the
models that explain the ankle as the transition from the galactic and
extragalactic components are disfavored by present data. Recently, it has been
proposed that this light component originates from the photodisintegration of
more energetic and heavier nuclei in the source environment. The formation of
the ankle can also be explained by this mechanism. In this work we study in
detail this general scenario but in the context of the central region of active
galaxies. In this case, the cosmic rays are accelerated near the supermassive
black hole present in the central region of these types of galaxies, and the
photodisintegration of heavy nuclei takes place in the radiation field that
surrounds the supermassive black hole.

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The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
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The categories of this paper are: cs
12
The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: q-alg
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom