Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chiral expansion of nucleon PDF at $x\sim m_\pi/M_N$   Based on the chiral perturbation theory, we investigate the low-energy
dynamics of nucleon parton distributions. We show that in different regions of
the momentum fraction $x$ the chiral expansion is significantly different. For
nucleon parton distributions these regions are characterized by $x\sim1$,
$x\sim m_\pi/M_N$ and $x\sim (m_\pi/M_N)^2$. We derive extended counting rules
for each region and obtain model-independent results for the nucleon parton
distributions down to $x\gtrsim m^2_\pi/M^2_N \approx 10^{-2}$.

16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
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The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an