Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variable-range-hopping conductivity of half-doped bilayer manganite
  LaSr$_{2}$Mn$_{2}$O$_{7}$   We report measurements of in-plane $\rho_{ab}$ and out-of-plane $\rho_{c}$
resistivities on a single crystal of the half-doped bilayer manganite
LaSr$_{2}$Mn$_{2}$O$_{7}$. In the temperature $T$ range 220 to 300 K, the
resistive anisotropy $\rho_{c}/\rho_{ab}=A+B/T$ ($A$ and $B$ constants), which
provides evidence for the variable-range-hopping conduction in the presence of
a Coulomb gap. This hopping mechanism also accounts for the quadratic magnetic
field $H$ and $\sin^{2}\phi$ dependences of the negative magnetoresistivity
$\ln [\rho_{i}(T,H,\phi)/\rho_{i}(T,H=0)]$ ($i=ab,c$), where $\phi$ is the
in-plane angle between the magnetic field and the current.

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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: econ
37
The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin