Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Recoil Correction to Hydrogen Energy Levels: A Revision   Recent calculations of the order (Z\alpha)^4(m/M)Ry pure recoil correction to
hydrogen energy levels are critically revised. The origins of errors made in
the previous works are elucidated. In the framework of a successive approach,
we obtain the new result for the correction to S levels. It amounts to -16.4
kHz in the ground state and -1.9 kHz in the 2S state.

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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: supr-con
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The categories of this paper are: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: econ
10
The categories of this paper are: q-bio