Shear transport far from equilibrium via holography

In heavy-ion collisions, the quark-gluon plasma is produced far from equilibrium. This regime is currently inaccessible by direct quantum chromodynamics (QCD) computations. In a holographic context, we propose a general method to characterize transport properties based on well-defined two-point functions. We calculate shear transport and entropy far from equilibrium, defining a time-dependent ratio of shear viscosity to entropy density, eta/s. Large deviations from its near-equilibrium value 1/4 pi, up to a factor of 2.5, are found for realistic situations at the Large Hadron Collider. We predict the far-from-equilibrium time-dependence of eta/s to substantially affect the evolution of the QCD plasma and to impact the extraction of QCD properties from flow coefficients in heavy-ion collision data. (C) 2020 The Author(s). Published by Elsevier B.V.