Publication: The ratio of viscosity to entropy density in a pion gas satisfies the KSS holographic bound
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2007-03
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Springer
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Abstract
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/(4 pi) bound. We find similar results with other sets of phase-shifts and conclude that the bound is nowhere violated.
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© EPJ, Springer Verlag, Societá Italiana di Fisica.
We thank Jochen Wambach for encouraging us to carry out this interesting calculation, Juan M. Torres Rincón for useful comments, and Angel Gomez Nicola, Daniel Fernandez Fraile and Dany Davesne for feedback on their own evaluation of transport coefficients in a pion gas. This work has been supported by grants FPA 2004-02602, 2005-02327, PR27/05-13955-BSCH (Spain).
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