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Perfect fluidity: from quark-gluon plasmas to ultra-cold Fermi gases


Recently, there has been tremendous interest in the viscosity of quantum fluids where the interactions between particles can be very strong.  In such liquids, the viscosity can be very small.  The study of the ultra low-viscosity ("perfect") fluids has brought together diverse areas of  physics--black holes and string theory, quark-gluon plasmas, quantum fluids and cold atoms--which appear to have little in common.  There is now a considerable effort devoted to understanding the universal properties of these perfect fluids, particularly the recent conjecture that there is a intrinsic quantum mechanical lower bound on the viscosity. I will review some of the experimental and theoretical developments in this field: exact results in dilute gases of neutral Fermi atoms with large s-wave scattering lengths, progress in finding a universal quantum lower bound  for the viscosity and what such a bound could teach us about conductivity in solid-state systems.