Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theory of electrostatically induced shape transitions in carbon
  nanotubes   A mechanically bistable single-walled carbon nanotube can act as a
variable-shaped capacitor with a voltage-controlled transition between
collapsed and inflated states. This external control parameter provides a means
to tune the system so that collapsed and inflated states are degenerate, at
which point the tube's susceptibility to diverse external stimuli--
temperature, voltage, trapped atoms -- diverges following a universal curve,
yielding an exceptionally sensitive sensor or actuator that is characterized by
a vanishing energy scale. For example, the boundary between collapsed and
inflated states can shift hundreds of Angstroms in response to the presence or
absence of a single gas atom in the core of the tube. Several potential
nano-electromechanical devices can be based on this electrically tuned
crossover between near-degenerate collapsed and inflated configurations.

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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: econ
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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: cmp-lg
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The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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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: atom-ph