Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Strongly Correlated Impurity Band Superconductivity in Diamond: X-ray
  Spectroscopic evidence for upper Hubbard and mid-gap bands   In a recent X-ray absorption study in boron doped diamond, Nakamura et al.
have seen a well isolated narrow boron impurity band in non-superconducting
samples and an additional narrow band at the chemical potential in a
superconducting sample. We interpret the beautiful spectra as evidence for
upper Hubbard band of a Mott insulating impurity band and an additional
metallic `mid-gap band' of a conducting `self-doped' Mott insulator. This
supports the basic framework of a recent theory of the present author of
strongly correlated impurity band superconductivity (SCIBS) in a template of a
wide-gap insulator, with no direct involvement of valence band states.

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The categories of this paper are: dg-ga
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The categories of this paper are: hep-th
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The categories of this paper are: ao-sci
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The categories of this paper are: bayes-an
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
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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: math
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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: nlin
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The categories of this paper are: funct-an
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The categories of this paper are: stat