Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Coherence lengths and anisotropy in MgB2 superconductor   Field and temperature microwave measurements have been carried out on MgB2
thin film grown on Al2O3 substrate. The analysis reveals the mean field
coherence length xi_{MF} in the mixed state and a temperature independent
anisotropy ratio gamma_{MF} = xi_{MF}^{ab} / xi_{MF}^c approximately 2. At the
superconducting transition, the scaling of the fluctuation conductivity yields
the Ginzburg-Landau coherence length with a different anisotropy ratio
gamma_{GL} = 2.8, also temperature independent.

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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: astro-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin
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The categories of this paper are: eess
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The categories of this paper are: hep-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph