Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultrathin Metallic Coatings Can Induce Quantum Levitation between
  Nanosurfaces   There is an attractive Casimir-Lifshitz force between two silica surfaces in
a liquid (bromobenze or toluene). We demonstrate that adding an ultrathin
(5-50{\AA}) metallic nanocoating to one of the surfaces results in repulsive
Casimir-Lifshitz forces above a critical separation. The onset of such quantum
levitation comes at decreasing separations as the film thickness decreases.
Remarkably the effect of retardation can turn attraction into repulsion. From
that we explain how an ultrathin metallic coating may prevent
nanoelectromechanical systems from crashing together.

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The categories of this paper are: math
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The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: eess