Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A New Limit on the Distances of Nuclei UHECRs Sources   Recent evidence from the Pierre Auger Observatory suggests a transition, at 5
EeV-10EeV in the composition of Ultra High Energy Cosmic Rays (UHECRs), from
protons to heavier nuclei such as iron. I consider here the implications of the
heavier composition on the sources of UHECRs. The smaller magnetic rigidity
implies that nuclei UHECRs are: (i) More easily accelerated (ii) Local, as they
can diffuse only a few Mpc from their sources before disintegrating (iii)
Isotropic, because large deflections in the extra galactic and the galactic
magnetic fields erase the directional information. Uncertainties in the
strength and structure of the the extra galactic magnetic field (EGMF) makes it
difficult to estimate the overall effects. However, with typical reasonable
parameters of a few nG and a coherence distance of a Mpc the distance a nuclei
UHECR above the GZK energy traverses before photodisintegrating is only a few
Mpc. In spite of the significantly weaker limits on the luminosity, Cen A is
the only currently active potential source of nuclei UHECRs within this
distance. The large deflections erases the directional anisotropy expected from
a single source. If indeed the composition of above-GZK-UHECRs is iron and if
the EGMF is not too small then Cen A is the dominant source of observed nuclei
UHECRs above the GZK limit.

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The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: patt-sol
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: adap-org
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: econ
1
The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: physics