Speaker
Description
Viscous hydrodynamics serves as a successful mesoscopic description of the quark-gluon plasma (QGP) produced in relativistic heavy-ion collisions (HICs). In order to investigate, how such an effective description emerges from the underlying microscopic dynamics we calculate the linear response of energy and flow perturbations in the sound and shear channels from a first-principle calculation in kinetic theory. By using both QCD kinetic theory and Relaxation Time Approximation we investigate the similarities and differences of the excitations in different microscopic theories and compare them to first and second order hydrodynamics. Surprisingly, we find that even for large gradients the Greens functions in QCD Kinetic theory are well described by one hydrodynamic and one non-hydrodynamic mode. We extract the dispersion relations of hydrodynamic and non-hyrodynamic modes and speculate how these results can be used to improve hydrodynamic descriptions of hot QCD matter.
