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


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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Correspondence to F.J. Llanes-Estrada.

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05.20.Dd; 51.20.+d

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Dobado, A., Llanes-Estrada, F. The ratio of viscosity to entropy density in a pion gas satisfies the KSS holographic bound. Eur. Phys. J. C 49, 1011–1013 (2007).

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  • Entropy Density
  • Chiral Perturbation Theory
  • Scatter Phase Shift
  • Average Momentum
  • Inverse Amplitude Method