Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Shear Viscosity to Entropy Density Ratio of Trapped Fermions in the
  Unitarity Limit   We extract the shear viscosity to entropy density ratio \eta/s of cold
fermionic atoms in the unitarity limit from experimental data on the damping of
collective excitations. We find that near the critical temperature \eta/s is
roughly equal to 1/2 in units of \hbar/k_B. With the possible exception of the
quark gluon plasma, this value is closer to the conjectured lower bound
1/(4\pi) than any other known liquid.

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The categories of this paper are: ao-sci
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The categories of this paper are: cmp-lg
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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: physics
2
The categories of this paper are: math
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga