Shear viscosity of a hadronic gas mixture
| dc.creator | Itakura, Kazunori | |
| dc.creator | Morimatsu, Osamu | |
| dc.creator | Otomo, Hiroshi | |
| dc.date | 2007-11-07 | |
| dc.date | 2007-11-16 | |
| dc.date.accessioned | 2026-07-07T11:54:03Z | |
| dc.date.available | 2026-07-07T11:54:03Z | |
| dc.description | 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. | |
| dc.description | 19 pages, 13 figures, reference added, figure 8 updated, minor change in the text | |
| dc.identifier | https://arxiv.org/abs/0711.1034 | |
| dc.identifier | http://arxiv.org/abs/0711.1034 | |
| dc.identifier | Phys.Rev.D77:014014,2008 | |
| dc.identifier | doi:10.1103/PhysRevD.77.014014 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/204761 | |
| dc.subject | High Energy Physics - Phenomenology | |
| dc.subject | Nuclear Theory | |
| dc.title | Shear viscosity of a hadronic gas mixture | |
| dc.type | text |