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

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 the bound is nowhere violated.

2 page text, three figures. V2: short comment and graph added to assert that a minimum of eta/s is not discarded from the hadron, low T side in a heavy-ion collision

References in corpus (4)

• Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics
• On the Strongly-Interacting Low-Viscosity Matter Created in Relativistic Nuclear Collisions
• Shear Viscosity to Entropy Density Ratio of QCD below the Deconfinement Temperature
• Low-Energy Thermal Photons from Meson-Meson Bremsstrahlung

Cited by in corpus (6)

• Shear viscosity of a hadronic gas mixture
• A sticky business: the status of the conjectured viscosity/entropy density bound
• $\eta /s$ and Phase Transitions
• The status of the KSS bound and its possible violations (How perfect can a fluid be?)
• On the violation of the holographic viscosity versus entropy KSS bound in non relativistic systems
• eta/s is critical (at phase transitions)