Physics – High Energy Physics – High Energy Physics - Phenomenology
Scientific paper
2007-11-07
Phys.Rev.D77:014014,2008
Physics
High Energy Physics
High Energy Physics - Phenomenology
19 pages, 13 figures, reference added, figure 8 updated, minor change in the text
Scientific paper
10.1103/PhysRevD.77.014014
We discuss in detail the shear viscosity coefficient eta and the viscosity to entropy density ratio eta/s of a hadronic gas comprised of pions and nucleons. In particular, we study the effects of baryon chemical potential on eta and eta/s. We solve the relativistic quantum Boltzmann equations with binary collisions (pi pi, pi N, and NN) for a state slightly deviated from thermal equilibrium at temperature T and baryon chemical potential mu. The use of phenomenological amplitudes in the collision terms, which are constructed to reproduce experimental data, greatly helps to extend the validity region in the T-mu plane. The total viscosity coefficient eta(T,mu)=eta^pi + eta^N increases as a function of T and mu, indirectly reflecting energy dependences of binary cross sections. The increase in mu direction is due to enhancement of the nucleon contribution eta^N while the pion contribution eta^pi diminishes with increasing mu. On the other hand, due to rapid growth of entropy density, the ratio eta/s becomes a decreasing function of T and mu in a wide region of the T-mu plane. In the kinematical region we investigated T < 180MeV, mu < 1GeV, the smallest value of eta/s is about 0.3. Thus, it never violates the conjectured lower bound eta/s= 1/4pi ~ 0.1. The smallness of eta/s in the hadronic phase and its continuity at T ~ T_c (at least for crossover at small mu) implies that the ratio will be small enough in the deconfined phase T > T_c. There is a nontrivial structure at low temperature and at around normal nuclear density. We examine its possible interpretation as the liquid-gas phase transition.
Itakura Kazunori
Morimatsu Osamu
Otomo Hiroshi
No associations
LandOfFree
Shear viscosity of a hadronic gas mixture does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Shear viscosity of a hadronic gas mixture, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Shear viscosity of a hadronic gas mixture will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-502341