Are these quasi-normal modes?

Abstract

We discuss how to extract numerically the expected lowest quasi-normal mode (QNM) associated with the pressure anisotropy for a Bjorken flux evolution to equilibrium. This QNM was easily decoded subtracting the hydrodynamical attractors and was compared with other authors calculations. After evolutions with transients close to the expected lowest QNM the system goes to a tail (pure imaginary frequency) for late times. We analyze the relevance of Navier-Stokes, second order and Borel attractors at each stage of the evolution, which begins far-from-equilibrium and ends close to equilibrium.