Apparent Thermalization due to Plasma Instabilities in Quark-Gluon Plasma

TL;DR

RHIC hydrodynamics suggests rapid onset of collective behavior around 0.6 fm/c, but this reflects fast isotropization rather than complete thermalization. The paper argues that non-Abelian plasma instabilities in an anisotropic quark-gluon plasma can drive exponential growth of soft gauge fields via collisionless Boltzmann-Vlasov dynamics, yielding isotropization at rates faster than perturbative scattering. As these soft fields grow to nonperturbative amplitudes, they induce large deflections of hard partons and drive the system toward isotropy on a timescale set by the instability growth rate, helping to reconcile weak-coupling expectations with early hydrodynamic behavior. The authors advocate for full 3D non-Abelian Boltzmann-Vlasov simulations to test and quantify this instability-driven isotropization scenario.

Abstract

Hydrodynamical modeling of heavy ion collisions at RHIC suggests that the quark-gluon plasma (QGP) "thermalizes" in a remarkably short time scale, about 0.6 fm/c. We argue that this should be viewed as indicating fast isotropization, but not necessarily complete thermalization, of the non-equilibrium QGP. Non-Abelian plasma instabilities can drive local isotropization of an anisotropic QGP on a time scale which is faster than ordinary perturbative scattering processes. As a result, we argue that theoretical expectations based on weak coupling analysis are not necessarily in conflict with hydrodynamic modeling of the early part of RHIC collisions, provided one recognizes the key role of non-Abelian plasma instabilities.