Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effective Action and Electromagnetic Polarizabilities of Nucleons in QCD
  String Theory   The effective action for baryons in the external electromagnetic fields is
obtained on the basis of the QCD string theory. The area law of the Wilson loop
integral, the approximation of the Nambu-Goto straight-line strings, and the
asymmetric quark-diquark structure of nucleons are used to simplify the
problem. The spin-orbit and spin-spin interactions of quarks are treated as a
perturbation. With the help of the virial theorem we estimate the mean radii of
nucleons in terms of the string tension and the Airy function zeros. On the
basis of the perturbation theory in small external electromagnetic fields we
derive the electromagnetic polarizabilities of nucleons. The electric and
diamagnetic polarizabilities of a proton are $\bar{\alpha}_p= 10\times 10^{-4}
fm^3$, $\beta_p^{dia}=-8\times 10^{-4} fm^3$ and for a neutron we find
$\bar{\alpha}_n=4.2\times 10^{-4} fm^3 $, $\beta_n^{dia}= -5.4\times 10^{-4}
fm^3$. Reasonable values of the magnetic polarizabilities $\bar{\beta}_p=(5\pm
3)\times 10^{-4} fm^3$, $\bar{\beta}_n=(7.6\pm 3)\times 10^{-4} fm^3$ are
estimated using the $\Delta$ contribution to the paramagnetic polarizability of
the nucleons.

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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: ao-sci
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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: math
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The categories of this paper are: hep-ex