https://doi.org/10.1140/epja/i2012-12142-2
Regular Article - Theoretical Physics
Chiral restoration effects on the shear viscosity of a pion gas
1
Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstr. 2, D-64289, Darmstadt, Germany
2
GSI Helmholtz-Zentrum für Schwerionenforschung, Planckstr. 1, D-64291, Darmstadt, Germany
* e-mail: michael.buballa@physik.tu-darmstadt.de
Received:
21
February
2012
Revised:
23
July
2012
Accepted:
20
September
2012
Published online:
22
October
2012
We investigate the shear viscosity of a pion gas in relativistic kinetic theory, using the Nambu-Jona-Lasinio model to construct the pion mass and the ππ-interaction at finite temperature. Whereas at low temperatures the scattering properties and, hence, the viscosity are in agreement with lowest-order chiral perturbation theory, we find strong medium modifications in the crossover region. Here the system is strongly coupled and the scattering lengths diverge, similarly as for ultra-cold Fermi gases at a Feshbach resonance. As a consequence, the ratio η/s is found to be strongly reduced as compared to calculations without medium-modified masses and scattering amplitudes. However, the quantitative results are very sensitive to the details of the applied approximations.
© SIF, Springer-Verlag Berlin Heidelberg, 2012
