Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anisotropic positive magnetoresistance of a nonplanar 2D electron gas in
  a parallel magnetic field   We study the transport properties of a 2D electron gas in narrow GaAs quantum
wells with AlAs/GaAs superlattice barriers. It is shown that the anisotropic
positive magnetoresistance observed in selectively doped semiconductor
structures in a parallel magnetic field is caused by the spatial modulation of
the 2D electron gas.

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The categories of this paper are: solv-int
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The categories of this paper are: math-ph
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: eess
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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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: mtrl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex