Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Density Matrix Renormalization Group Study of Ultrasmall
  Superconducting Grains   We apply the DMRG method to the BCS pairing Hamiltonian which describes
ultrasmall superconducting grains. Our version of the DMRG uses the particle
(hole) states around the Fermi level as the system block (environment). We
observe a smooth logarithmic-like crossover between the few electron regime and
the BCS-bulk regime.

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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: physics
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The categories of this paper are: stat
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: eess