Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonradiative Recombination of Excitons in Carbon Nanotubes Mediated by
  Free Charge Carriers   Free electrons or holes can mediate the nonradiative recombination of
excitons in carbon nanotubes. Kinematic constraints arising from the quasi
one-dimensional nature of excitons and charge carriers lead to a thermal
activation barrier for the process. However, a model calculation suggests that
the rate for recombination mediated by a free electron is the same order of
magnitude as that of two-exciton recombination. Small amounts of doping may
contribute to the short exciton lifetimes and low quantum yields observed in
carbon nanotubes.

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The categories of this paper are: cs
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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: chem-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: math-ph
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The categories of this paper are: adap-org