Shear viscosity of hot nuclear matter by the mean free path method

Abstract

The shear viscosity of hot nuclear matter is investigated by using the mean free path method within the framework of IQMD model. Finite size nuclear sources at different density and temperature are initialized based on the Fermi-Dirac distribution. The results show that shear viscosity to entropy density ratio decreases with the increase of temperature and tends toward a constant value for $\rho\sim\rho_0$, which is consistent with the previous studies on nuclear matter formed during heavy-ion collisions. At $\rho\sim\frac{1}{2}\rho_0$, a minimum of $\eta/s$ is seen at around $T=10$ MeV and a maximum of the multiplicity of intermediate mass fragment ($M_{\text{IMF}}$) is also observed at the same temperature which is an indication of the liquid-gas phase transition.Comment: 5 figs and 5 pages; accepted by Physical Review

Similarity between the kinematic viscosity of quark-gluon plasma and liquids at the viscosity minimum

“…The minimum in this picture is related to the breakdown of the hydrodynamics expansion [30]. A minimum for η/s was also discussed in holographic models where it corresponds to a transition between thermal gas background and a big black hole solution at high temperature [31], and in certain nuclear matter models [32,33].…”

Report on scipost_202012_00017v1

“…The minimum in this picture is related to the breakdown of the hydrodynamics expansion [29]. A minimum for η/s was also discussed in holographic models where it corresponds to a transition between thermal gas background and a big black hole solution at high temperature [30], and in certain nuclear matter models [31,32].…”

Determining the temperature in heavy-ion collisions with multiplicity distribution

“…For a groundstate nucleus, we generate A Gaussian wave-packets, with their spatial center r i (t = 0) sampled randomly within a sphere of radius given by r 0 A 1/3 with r 0 = 1.12 fm, and their momentum center p i (t = 0) sampled following the zero-temperature Fermi-Dirac distribution. A finite nucleus at a given temperature T can be generated by sampling p i (t = 0) according to finite temperature Fermi-Dirac distribution [19], which is given by,…”

“…At zero temperature, the properties of nuclear matter have been studied extensively, and its equation of state (EOS), including its isospin dependence, i.e., symmetry energy, has been determined relatively well [1][2][3], while its properties at finite temperature are relatively little touched upon. Among these properties, two noticeable examples are the nuclear liquid-gas phase transition [4][5][6][7][8][9][10][11][12][13][14][15][16] and the temperature dependence of the ratio of shear viscosity to entropy density (η/s) [17][18][19][20][21][22]. The latter is also connected to the nuclear giant dipole resonance at finite temperature [23][24][25], since both of them are related to the two-body dissipation of nucleons.…”