| Popis: |
The ratio κ of the shear viscosity η to the volume density of entropy s , κ = η / s , of the rare gases He, Ne, Ar, Kr, and Xe and the molecules H 2 , N 2 , CH 4 , and CF 4 is studied in the critical region. It is shown that the minimum value κ m of η / s is observed in the vicinity of the critical point. In addition the universal inequality κ ⩾ ℏ / ( 4 π k ) proposed by Kovtun et al. (2005) holds for these gases. For the rare gases and 6Li κ m depends linearly on m 1 / 2 σ 2 , where m is the mass and σ defined via the potential energy function as U ( σ ) = 0 . κ m of the molecules H 2 , N 2 , CH 4 , and CF 4 falls on the same straight line provided that the vibrational and rotational contributions to the entropy density s are removed. |
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