Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Vortex creep and critical current densities in superconducting
  (Ba,K)Fe$_{2}$As$_{2}$ single crystals   The surprisingly rapid relaxation of the sustainable current density in the
critical state of single crystalline Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ is
investigated for magnetic fields oriented parallel to the c-axis and to the
$ab$--plane respectively. Due to the inadequacy of standard analysis procedures
developed for flux creep in the high temperature superconducting cuprates, we
develop a simple, straightforward data treatment technique that reveals the
creep mechanism and the creep exponent $\mu$. At low magnetic fields, below the
second magnetization peak, $\mu$ varies only slightly as function of
temperature and magnetic flux density $B$. From the data, we determine the
temperature- and field dependence of the effective activation barrier for
creep. At low temperatures, the measured current density approaches the
zero--temperature critical current density (in the absence of creep) to within
a factor 2, thus lending credence to earlier conclusions drawn with respect to
the pinning mechanism. The comparable values of the experimental screening
current density and the zero-temperature critical current density reveals the
limited usefulness of the widely used "interpolation formula".

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The categories of this paper are: q-alg
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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
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The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
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The categories of this paper are: math
24
The categories of this paper are: dg-ga
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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-bio