Beyond the wake: Hydrodynamic and non-hydrodynamic response of an expanding Quark-gluon plasma to a moving energetic probe

<!--HTML-->We study the response of a Bjorken-expanding quark-gluon plasma (QGP) to the passage of an energetic parton through it. We compute the non-equilibrium stress-energy tensor induced by such moving energetic parton using linearized Boltzmann equation under the relaxation time approximation. At large distances and large Bjorken time, the QGP exhibits hydrodynamic response, meaning the disturbance induced by the energetic parton forms a Mach cone and diffusive wake. However, the transition from hydrodynamic response to non-hydrodynamic response occurs at the intermediate distances and times. We will characterize the features of the non-hydrodynamic response due to the competition among multiple time scales of the problem: the expansion rate of the medium, the equilibration rate of the medium and the rate of energy/momentum loss of the energetic parton. Finally, we will discuss the phenomenological implication of our study.