DEPARTMENT COLLOQUIUM | The Tyranny of Asymptotic Freedom

The discovery by Gross, Politzer and Wilczek in the early 1970’s of asymptotic freedom in quantum chromodynamics transformed our understanding of the strong interaction. In particular, it led to predictions that hot dense nuclear matter should form a quark-gluon plasma composed of “free” quarks and gluons. While lattice quantum chromodynamics gave some support for this view, experimental evidence for quark-gluon plasma (QGP) was ambiguous at best. This changed dramatically in 2000 with first data from the Relativistic Heavy Ion Collider, which demonstrated that a) the requisite very high temperatures and densities had been achieved, b) the produced matter did not behave as a quasi-ideal state of free quarks and gluons but rather c) the matter is a dense fluid with very low kinematic viscosity, approaching a conjectured viscosity bound obtained via the gauge/gravity duality. As such, the “strongly-coupled QGP” is most perfect fluid ever studied in the laboratory. Heavy ion collisions at the LHC have confirmed and extended these observations. In addition to presenting the key results and insights, I will also discuss the conceptual errors that led to the prediction of quasi-free behavior for the QGP.

Department Colloquia listings for Winter 2014.