Los Alamos National Laboratory, September 14, 1:00 pm
Extending the hydrodynamic description of the quark-gluon plasma
The quark-gluon plasma (QGP) is a hot and dense state of matter governed by the quantum chromodynamics (QCD). Like many other QCD systems, QGP displays different properties when probed at different length scales. At long wavelengths or small gradients, it turns out to be a nearly perfect liquid; while at short distances, one expects to resolve quarks and gluons in the plasma. However, the dynamics at the intermediate length scale and how it transits from hydrodynamic to microscopic excitations are relatively less discussed. Recently, we noticed that in both weakly-coupled and strongly-coupled proxy theories of the QGP, sound modes continue to dominate the response at large wavenumbers, way beyond the traditional hydrodynamic region. I will demonstrate how we extend the Muller-Israel-Stewart hydrodynamic equations to describe such “sound dominance” of the linear response of the system at large gradients. Finally, I will discuss possible phenomenological applications in heavy-ion collisions.