Colloquia

The quark-gluon plasma produced in relativistic heavy ion collisions has been found to behave like a low viscosity fluid whose properties are very different from those of a weakly interacting gas of quarks and gluons. It is an example of a strongly coupled, strongly correlated system, for which perturbative approximation techniques are not adequate. However, it is now understood that certain 3+1 dimensional gauge theories, similar to QCD, may be exactly reformulated as string theories in higher dimensions --- and this "gauge/string duality" is easiest to use in the strongly coupled limit of the gauge theory. Under this duality, properties of a high temperature, strongly coupled plasma are directly related to gravitational dynamics around 4+1 dimensional black holes. Using this duality, it is possible to compute, reliably, dynamical properties such as viscosity, energy loss of heavy particles, and emission spectra in certain strongly coupled gauge theory plasmas. This talk will describe this progress and discuss its applicability to the quark-gluon plasma produced in current and upcoming experiments.