Speaker
Description
When two heavy nuclei collide in relativistic heavy ion collisions, the resulting
system is initially in a non-equilibrium state. The evolution of the system
towards equilibrium can be studied by using the Boltzmann equation.
However, approximating the solution to the Boltzmann equation using a
gradient expansion leads to a divergent series. Using an integral solution to
the Boltzmann equation in relaxation time approximation, we obtain its full
gradient expansion which contains exponentially decaying non-hydrodynamic
terms. It is shown that this gradient expansion can have a finite radius of
convergence. We further argue that, in the relaxation time model, proximity
to local thermal equilibrium is not necessary for the system to be described by
hydrodynamic equations.
