Shear viscosity to entropy density ratio of QCD below the deconfinement temperature
Journal
Physics Letters
Journal Volume
B647
Pages
371-375
Date Issued
2006-04
Author(s)
Nakano, Eiji
Abstract
Using chiral perturbation theory we investigate the QCD shear viscosity (η) to entropy density (s) ratio below the deconfinement temperature (∼170MeV) with zero baryon number density. It is found that η/s of QCD is monotonically decreasing in temperature (T) and reaches 0.6 with estimated ∼50% uncertainty at T=120MeV. A naive extrapolation of the leading order result shows that η/s reaches the 1/4π minimum bound proposed by Kovtun, Son, and Starinets using string theory methods at T∼200MeV. This suggests a phase transition or cross over might occur at T≲200MeV in order for the bound to remain valid. Also, it is natural for η/s to stay close to the minimum bound around the phase transition temperature as was recently found in heavy ion collisions.
Type
journal article