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Starting from relativistic quantum field theories, Kovtun et al.(2005) have quite recently proposed a lower bound η/s⩾ ℏ/(4 π k B), where η is the shear viscosity and s the volume density of entropy for dense liquids. If their proposal can eventually be proved, then this would provide key theoretical underpinning to earlier semiempirical proposals on the relation between a transport coefficient η and a thermodynamic quantity s. Here, we examine largely experimental data on some dense liquids, the insulators nitrogen, water, and ammonia, plus the alkali metals, where the shear viscosity η (T) for the four heaviest alkalis is known to scale onto an ‘almost universal’curve, following the work of Tankeshwar and March a decade ago. So far, all known results for both insulating and metallic dense liquids correctly exceed the lower bound prediction of Kovtun et al.
Publication date: 
2 Mar 2009

GGN Angilella, NH March, FMD Pellegrino, R Pucci

Biblio References: 
Volume: 373 Issue: 10 Pages: 992-998
Physics Letters A