Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultrahigh-Energy Neutrino-Nucleon Cross Sections and Perturbative
  Unitarity   Unitarity relates the total cross section for neutrino-nucleon scattering to
the neutrino-nucleon forward scattering amplitude. Assuming the validity of the
perturbative expansion of the forward amplitude in the {\em weak} coupling
constant, we derive a unitarity bound on the inelastic cross section. The
inelastic cross section saturates this bound at a typical neutrino energy
$E_\nu \simeq 10^8 {\rm GeV}$. This implies that calculations of the inelastic
cross section that use current parton distribution functions and lowest order
weak perturbation theory are unreliable above this energy.

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The categories of this paper are: quant-ph
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The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
2
The categories of this paper are: math
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The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom