Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Noncommutativity of Space and Rotation of Polarization of Light in a
  Background Magnetic Field   Recently the PVLAS collaboration has reported the observation of rotation of
polarization of light propagating in a background magnetic field. In this
letter we explore the possibility that such a rotation is a result of
noncommutativity in the background space-time. To explain the reported
polarization rotation within noncommutative QED we need the noncommutativity
parameter $\theta\simeq (30 {\rm GeV})^{-2}$.

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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
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The categories of this paper are: chem-ph