Regular Article - Theoretical Physics
The ratio of viscosity to entropy density in a pion gas satisfies the KSS holographic bound
Departamento de Física Teórica I, Universidad Complutense, 28040, Madrid, Spain
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Revised: 30 October 2006
Published online: 11 January 2007
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.
© Springer-Verlag Berlin Heidelberg, 2007