Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comment on the paper: ``Feynman-Schwinger representation approach to
  nonperturbative physics'' by C. Savkli et al. [Phys. Rev. C 60, 055210
  (1999), hep-ph/9906211]   We point out that the scalar Wick-Cutkosky model (with $\chi^2 \phi$
interaction) used in this study has been known for a long time to be unstable.
However, the numerical results presented in this paper do not show any sign of
this instability which casts some doubt on their reliability. We compare with
the worldline variational approach.

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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: stat
3
The categories of this paper are: physics
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The categories of this paper are: hep-th
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The categories of this paper are: astro-ph
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The categories of this paper are: econ
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The categories of this paper are: chao-dyn
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The categories of this paper are: dg-ga
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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: bayes-an
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The categories of this paper are: gr-qc