The Perfect Liquid - Now Even More Perfect

Previous theories imposed a limit on how "liquid" fluids can be. Recent results at the Vienna University of Technology suggest that this limit can be broken by a quark-gluon plasma, generated by heavy-ion collisions in particle accelerators. How liquid can a fluid be? This is a question particle physicists at the Vienna University of Technology have been working on. The "most perfect liquid" is nothing like water, but the extremely hot quark-gluon-plasma which is produced in heavy-ion collisions at the Large Hadron Collider at CERN. New theoretical results at Vienna UT show that this quark-gluon plasma could be even less viscous than was deemed possible by previous theories. The results were published in "Physical Review Letters" and highlighted as an "editors' selection". Liquids and their Viscosity Highly viscous liquids (such as honey) are thick and have strong internal friction, quantum liquids, such as super fluid helium can exhibit extremely low viscosity. In 2004, theorists claimed that quantum theory provided a lower bound for viscosity of fluids. Applying methods from string theory, the lowest possible ratio of viscosity to the entropy density was predicted to be -/4? (with the Planck-constant -). Even super fluid helium is far above this threshold. In 2005, measurements showed that quark-gluon-plasma exhibits a viscosity just barely above this limit. However, this record for low viscosity can still be broken, claims Dominik Steineder from the Institute for Theoretical Physics at Vienna UT. He obtained this remarkable result working as a PhD-student with Professor Anton Rebhan. Black Holes and Particle Collisions