Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Expectation values of four-quark operators in pions   The values of four-quark operators averaged over pions are expressed through
those averaged over vacuum. The specific values are obtained in the framework
of the factorization assumption. For the condensates of the light quarks of the
same flavour \bar q\Gamma q\bar q\Gamma q the scalar condensate is shown to be
an order of magnitude larger than the other ones. The condensates containing
the strange quarks \bar q q\bar s s appear to be only about twice smaller than
those of the light quarks. The degeneracy of the ground state in the
Nambu--Jona--Lasinio model is shown explicitly.

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The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
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The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
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The categories of this paper are: alg-geom