GLYPH<s48>GLYPH<s46>GLYPH<s48> GLYPH<s48>GLYPH<s46>GLYPH<s53> GLYPH<s49>GLYPH<s46>GLYPH<s48> GLYPH<s49>GLYPH<s46>GLYPH<s53> GLYPH<s50>GLYPH<s46>GLYPH<s48> GLYPH<s50>GLYPH<s46>GLYPH<s53> GLYPH<s48>GLYPH<s46>GLYPH<s48>GLYPH<s48> GLYPH<s48>GLYPH<s46>GLYPH<s48>GLYPH<s50> GLYPH<s48>GLYPH<s46>GLYPH<s48>GLYPH<s52> GLYPH<s48>GLYPH<s46>GLYPH<s48>GLYPH<s54> GLYPH<s48>GLYPH<s46>GLYPH<s48>GLYPH<s56> GLYPH<s48>GLYPH<s46>GLYPH<s49>GLYPH<s48> GLYPH<s32> GLYPH<s47> GLYPH<s115> GLYPH<s116>GLYPH<s32>GLYPH<s40>GLYPH<s102>GLYPH<s109> GLYPH<s47>GLYPH<s99> GLYPH<s41> GLYPH<s98>GLYPH<s61>GLYPH<s56>GLYPH<s46>GLYPH<s54>GLYPH<s32>GLYPH<s102> GLYPH<s109> GLYPH<s97>GLYPH<s116> GLYPH<s32>GLYPH<s116> GLYPH<s104>GLYPH<s101>GLYPH<s32>GLYPH<s99>GLYPH<s111>GLYPH<s108>GLYPH<s108>GLYPH<s105>GLYPH<s115>GLYPH<s105>GLYPH<s111>GLYPH<s110>GLYPH<s32>GLYPH<s99>GLYPH<s101>GLYPH<s110>GLYPH<s116> GLYPH<s101>GLYPH<s114> GLYPH<s32> GLYPH<s100> GLYPH<s71> GLYPH<s61>GLYPH<s49>GLYPH<s54> GLYPH<s32> GLYPH<s100> GLYPH<s71> GLYPH<s61>GLYPH<s52>GLYPH<s48> FIG. 9: (Color online) Time evolution of the ratio of the shear viscosity to the entropy density. number of parton degrees of freedom, therefore, the difference in η/s comes mainly from the different chemical equilibration in two calculations, i.e., the difference in fugacity λ , which appears in Eq. (17) as 1 . 5 R$_{gg}$$_{→}$$_{ggg}$ − R$_{ggg}$$_{→}$$_{gg}$ ≈ 1 . 5(1 − λ ) R$_{gg}$$_{→}$$_{ggg}$ and in Eq. (18) as ln λ . In Fig. 10 we see that the parton fugacity λ ( t ) of the system with d$_{G}$ = 40 is smaller than that with d$_{G}$ = 16 due to the increase of parton degrees of freedom after the initial production. Smaller λ decreases η and increases s , and, thus, decreases the η/s ratio, especially at early times when the system is far from the chemical equilibrium. We note that the total entropy density of the quark and gluon system can only be calculated via Eq. (18), if the λ values of quarks and gluons are the same. In the reality, gluons dominate the early stage of the plasma and the gluon fugacity should be larger than the quark’s. Therefore, the true entropy density is smaller than that obtained via Eq. (18). The true η/s ratio of a quark gluon plasma should be larger than that presented as the dashed curve and thus may become closer to the values for a pure gluon plasma. Moreover, the contribution of the chemical equilibration to η , the term 1 . 5 R$_{gg}$$_{→}$$_{ggg}$ − R$_{ggg}$$_{→}$$_{gg}$ in Eq. (17), does not appear explicitly in the expression derived in Ref. [37] by using the second order Grad’s expansion. This may slightly increase η compared to the Navier-Stokes value via Eq. (17), if the system is out of chemical equilibrium. 15