Speaker
Summary
We report novel results on the characterization of the evolution of a Bjorken expanding medium. Within the framework of kinetic theory, we introduce the generalized notion of "adiabatic approximation" under which the bulk evolution is driven by a specific set of slow modes. We show that those slow modes correspond to the shape of the (appropriately weighted) equal-probability surface of gluon distribution in the phase (momentum) space, and they will gradually evolve into hydrodynamic modes at late time.
For this reason, the behavior analogous to a fluid emerges even at an early time, We
demonstrate how "adiabatic approximation" could be employed as a unified scheme to describe equally the pre-equilibrium stage as well as the hydrodynamical stage.
To support our claim, we present a parametric analysis based on bottom-up thermalization scenario to show the applicability of "adiabatic approximation" during the course of thermalization. In addition to this qualitative discussion, we verify quantitatively that such approximation describes well the bulk evolution determined from solutions of the kinetic equation under relaxation time approximation. Remarkably, the zeroth order adiabatic approximation result is systematically improved when the first order contribution is included.
