Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutral pion mass in the linear sigma model coupled to quarks at
  arbitrary magnetic field   We calculate the neutral pion mass in the presence of an external magnetic
field of arbitrary strength in the framework of the linear sigma model coupled
to quarks at zero temperature. We find nonmonotonic behavior of the pion mass
as a function of magnetic field. We are also able to reproduce existing results
for the weak-field approximation.

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The categories of this paper are: quant-ph
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The categories of this paper are: supr-con
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: cs
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The categories of this paper are: funct-an
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The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: chao-dyn