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Recall that in the last section, it was argued that the region µ/T > 11 . 7 is unphys- ical, or perhaps metastable, since the entropy increases with decreasing temperature there. Thus for the regions that are surely physical, the bound (76) holds. It is nevertheless interesting to study the viscosity in this unphysical region. In the zero temperature limit, i.e. T/µ → 0 $^{+}$, η/s slowly decreases and seems to approach the bound. See Figure 11. However it eventually dips below it. See Figure 12. This behavior can be understood analytically as follows. For x = µ/T very large, the solution to the equation (53) is approximately: 

This leads to the asymptotic expansions: 

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