Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nearly Perfect Fluidity in a High Temperature Superconductor   Perfect fluids are characterized as having the smallest ratio of shear
viscosity to entropy density, {\eta}/s, consistent with quantum uncertainty and
causality. So far, nearly perfect fluids have only been observed in the
Quark-Gluon Plasma (QGP) and in unitary atomic Fermi gases (UFG), exotic
systems that are amongst the hottest and coldest objects in the known universe,
respectively. We use Angle Resolve Photoemission Spectroscopy (ARPES) to
measure the temperature dependence of an electronic analogue of {\eta}/s in an
optimally doped cuprate high temperature superconductor, finding it too is a
nearly perfect fluid around, and above, its superconducting transition
temperature Tc.

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The categories of this paper are: plasm-ph
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The categories of this paper are: math-ph
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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: cs
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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: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: econ
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The categories of this paper are: eess
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The categories of this paper are: q-fin