Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Casimir spring and compass: Stable levitation and alignment of compact
  objects   We investigate a stable Casimir force configuration consisting of an object
contained inside a spherical or spheroidal cavity filled with a dielectric
medium. The spring constant for displacements from the center of the cavity and
the dependence of the energy on the relative orientations of the inner object
and the cavity walls are computed. We find that the stability of the force
equilibrium can be predicted based on the sign of the force, but the torque
cannot be.

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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: solv-int
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg
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The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
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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: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-th