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

2006/09/30 by Antonio Dobado, Felipe J. Llanes-Estrada, Felipe J. Llanes–Estrada · 2 citations
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph

paper · pdf · doi:10.1140/epjc/s10052-006-0176-4

published as Eur.Phys.J.C49:1011-1013,2007 · 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

arxiv created 2006/10/30 · openalex publication_date 2007/01/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01

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.

Citations

• Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics

Cited by

• The Status of the KSS Bound and its Possible Violations (How Perfect Can a Fluid Be?)
• A sticky business: the status of the conjectured viscosity/entropy density bound