Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Convergent close-coupling calculations of two-photon double ionization
  of helium   We apply the convergent close-coupling (CCC) formalism to the problem of
two-photon double ionization of helium. The electron-photon interaction is
treated perturbatively whereas the electron-electron interaction is included in
full. The integrated two-photon double ionization cross-section is
substantially below non-perturbative literature results. However, the pattern
of the angular correlation in the two-electron continuum is remarkably close to
the non-perturbative time-dependent close-coupling calculation of Hu {\em et
al} [J. Phys. {\bf B38}, L35 (2005)]

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The categories of this paper are: eess
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: supr-con
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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: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ph