Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Weak and Repulsive Casimir Force in Piston Geometries   We study the Casimir force in piston-like geometries semiclassically. The
force on the piston is finite and physical, but to leading semiclassical
approximation depends strongly on the shape of the surrounding cavity. Whereas
this force is attractive for pistons in a parallelepiped with flat cylinder
head, for which the semiclassical approximation by periodic orbits is exact,
this approximation to the force on the piston vanishes for a semi-cylindrical
head and becomes repulsive for a cylinder of circular cross section with a
hemispherical head. In leading semiclassical approximation the sign of the
force is related to the generalized Maslov index of short periodic orbits
between the piston and its casing.

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The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
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The categories of this paper are: cs
37
The categories of this paper are: supr-con
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: math
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The categories of this paper are: hep-ex
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The categories of this paper are: adap-org