Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: C-axis negative magnetoresistance and upper critical field of
  Bi2Sr2CaCu2O8   The out-of-plane resistance and the resistive upper critical field of
BSCCO-2212 single crystals with Tc=91-93 K have been measured in magnetic
fields up to 50 T over a wide temperature range. The results are characterised
by a positive linear magnetoresistance in the superconducting state and a
negative linear magnetoresistance in the normal state. The zero field normal
state c-axis resistance, the negative linear normal state magnetoresistance,
and the divergent upper critical field Hc2(T)are explained in the framework of
the bipolaron theory of superconductivity.

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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ph
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The categories of this paper are: math
35
The categories of this paper are: mtrl-th
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The categories of this paper are: stat