Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lamb shift calculated by simple noncovariant method   The Lamb Shift (LS) of Hydrogenlike atom is evaluated by a simple method of
quantum electrodynamics in noncovariant form, based on the relativistic
stationary Schr\"odinger equation. An induced term proportional to
$\overrightarrow{p}^4$ in the effective Hamiltonian is emphasized. Perturbative
calculation of second order leads to the LS of $ 1S_{1/2}$ state and that of
$2S_{1/2}-2P_{1/2}$ states in H atom with the high accuracy within 0.1%

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The categories of this paper are: physics
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The categories of this paper are: nucl-th
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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: atom-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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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: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-ex