Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Parton Distribution Functions   Parton distribution functions give the probability to find partons (quarks
and gluons) in a hadron as a function of the fraction x of the proton's
momentum carried by the parton. They are conventionally defined in terms of
matrix elements of certain operators. They are determined from experimental
results on short distance scattering of the partons. Integrals of these
functions weighted with x^n are calculable using lattice QCD. Some simple
models for their behavior have implications that could also be tested in
lattice QCD.

13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: mtrl-th