Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Critical Current Density in Polycrystalline HTS and LTS
  Superconductors in High Magnetic Fields   Flux pinning scaling laws were developed to explain the observed increase in
the critical current density Jc caused by increased density of grain boundaries
in polycrystalline low temperature superconductors (LTS) such as Nb3Sn. For
four decades they have provided the framework for the successful development of
the LTS materials that carry high Jc in high magnetic fields. However, the
discovery of the weak-link problem suggested that transmission of supercurrent
flow through the grain boundaries limited Jc in high temperature
superconductors (HTS) such as YBa2Cu3O7-{\delta} (YBCO). Here we provide
evidence that a single mechanism - flux flow along grain boundaries - confirmed
by time-dependent Ginzburg-Landau (TDGL) computational visualisation in LTS
materials, explains the functional form of Jc in polycrystalline LTS Nb3Sn and
HTS YBCO and (Bi,Pb)2Sr2Can-1CunOx (BiSCCO) materials in low and high magnetic
fields. Data presented show that standard flux pinning theory cannot explain
comprehensive Jc data for YBCO because Jc is a function of strain but the
superconducting properties are not. We conclude that grain boundaries are
narrow and metallic in Nb3Sn and YBCO but wide and semiconducting in BiSCCO.
Strain alters Jc by changing the superconducting properties of the grains in
Nb3Sn but by changing the grain boundaries in YBCO

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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ph
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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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: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
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The categories of this paper are: eess
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The categories of this paper are: hep-lat
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The categories of this paper are: cs