Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comment on "$\sigma$-meson: Four-quark versus two-quark components and
  decay width in a Bethe-Salpeter approach"   In a recent paper by N. Santowsky et al. [Phys. Rev. D 102, 056014 (2020)],
covariant coupled equations were derived to describe a tetraquark in terms of a
mix of four-quark states $2q 2\bar{q}$ and two-quark states $q\bar{q}$. These
equations were expressed in terms of vertices describing the disintegration of
a tetraquark into identical two-meson states, into a diquark-antidiquark pair,
and into a quark-antiquark pair. We show that these equations are inconsistent
as they imply a $q\bar{q}$ Bethe-Salpeter kernel that is $q\bar{q}$-reducible.

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The categories of this paper are: quant-ph
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The categories of this paper are: q-fin
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The categories of this paper are: eess
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The categories of this paper are: atom-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: math
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin
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The categories of this paper are: physics
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph