Adiabatic hydrodynamization in the bottom-up thermalization scenario*

In this talk we demonstrate that the early stages of the bottom-up thermalization scenario are well described by the adiabatic hydrodynamization framework. All of the qualitative features exhibited in QCD effective kinetic theory (EKT) simulations at weak coupling are captured by the emergence of an effective low-energy instantaneous ground state for the 1-particle gluon distribution function, which defines the early-time kinetic theory attractor. This ground state may be pulled back to arbitrarily early times, where it represents a free-streaming solution, and at later times it integrally describes the BMSS fixed point, including the recently observed deviations from the original predictions for the scaling exponents.

We proceed by studying scaling in the small-angle scattering approximation of QCD EKT. We find that a momentum rescaling allows the scaling distribution to be identified as the instantaneous ground state of the evolution of the distribution function, and the approach to the scaling function is described by the decay of the excited states. Corrections to the BMSS fixed point exponents agree quantitatively with previous numerical studies.