The ratio of viscosity to entropy density in a pion gas satisfies the KSS holographic bound

@article{Dobado2006TheRO,
  title={The ratio of viscosity to entropy density in a pion gas satisfies the KSS holographic bound},
  author={Antonio Dobado and Felipe J. Llanes-Estrada},
  journal={The European Physical Journal C},
  year={2006},
  volume={49},
  pages={1011-1013}
}
We evaluate the ratio of shear viscosity to entropy density in a pion gas employing the Uehling–Uehlenbeck equation and experimental phase-shifts parameterized by means of the SU(2) inverse amplitude method. We find that the ratio for this monocomponent gas stays well above the KSS 1/(4π) bound. We find similar results with other sets of phase-shifts and conclude that the bound is nowhere violated. 
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