# 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.

## 5 Citations

On the violation of the holographic viscosity versus entropy KSS bound in non-relativistic systems

- Physics
- 2007

A computation of the quotient of shear viscosity and entropy density, or the Kovtun, Son and Starinets (KSS) number η/s, is performed in the non-relativistic and classical regime, first in chiral…

η/s is critical (at phase transitions)

- Physics
- 2009

The viscosity over entropy density ratio, or KSS number, can help isolate the critical point in the hadron phase‐diagram in Relativistic Heavy Ion Collisions. We argue that this quantity does have a…

Transport coefficients of a hot QCD medium and their relative significance in heavy-ion collisions

- Physics
- 2017

The main focus of this article is to obtain various transport coefficients for a hot QCD medium that is produced while colliding two heavy nuclei ultra-relativistically. As the hot QCD medium follows…

The Status of the KSS Bound and its Possible Violations (How Perfect Can a Fluid Be

- Physics
- 2008

In this work we briefly review the Kovtun‐Son‐Starinet (KSS) computation of the ratio η/s for quantum field theories with gravitational dual and the related conjecture that it is bound from below by…

A sticky business: the status of the conjectured viscosity/entropy density bound

- Mathematics
- 2008

There have been a number of forms of a conjecture that there is a universal lower bound on the ratio, η/s, of the shear viscosity, η, to entropy density, s, with several different domains of…

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