We numerically solve the ($2+1$)-dimensional effective kinetic theory of weak coupling QCD under longitudinal expansion, relevant for early stages of heavy-ion collisions. We find agreement with viscous hydrodynamics and classical Yang-Mills simulations in the regimes where they are applicable. By choosing initial conditions that are motivated by a color-glass-condensate framework, we find that for $Q_s=2\mathrm{GeV}$ and ${\alpha }_s=0.3$ the system is approximately described by viscous hydrodynamics well before $\tau \lesssim 1.0\mathrm{fm}/c$.

• Received 14 July 2015

DOI:https://doi.org/10.1103/PhysRevLett.115.182301

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Published by the American Physical Society