Recently, the heavy-ion physics community has been interested in understanding the emergence of hydrodynamic behavior in far-from-equilibrium fluids (e.g. quark-gluon plasma formed in heavy-ion collisions). Conventionally, hydrodynamics is a small gradient expansion that should only work for near-equilibrium fluids. However, the success of viscous hydrodynamic simulations of heavy-ion collisions forces us to revisit this assumption. Here, we present a new way of deriving hydrodynamics from the Boltzmann equation in the relaxation time approximation. Our approach expands the Green’s function of the Boltzmann distribution to generate the hydrodynamic gradient series along with nonperturbative corrections. These nonperturbative terms strongly suppress high-order viscous corrections to the energy-momentum tensor of conformal systems subject to Bjorken flow. From the new expansion, we also derive i) a set of hydrodynamic equations capable of modeling kinetic systems far from equilibrium and ii) an alternative method for constructing the hydrodynamic attractor in Bjorken expansion.
Zoom link: https://osu.zoom.us/j/93062863602?pwd=anZmS25HMDdvYTNxamVZWjlBMXloQT09
Passcode: 145084
