The nonequilibrium evolution in a boost-invariant Bjorken flow of a hybrid viscous fluid model containing two interacting components with different viscosities, such that they represent strongly and weakly self-coupled sectors, is shown to be characterized by a hydrodynamic attractor which has an early-time behavior that is reminiscent of the so-called bottom-up thermalization scenario in heavy-ion collisions. The hydrodynamization times for the two sectors can differ strongly, with details depending on the curve realized on the two-dimensional attractor surface, which might account for different scenarios for small and large systems in nuclear collisions. The total system behaves as a single viscous fluid with a dynamically determined effective shear viscosity.

• Received 22 June 2020
• Accepted 12 November 2020

DOI:https://doi.org/10.1103/PhysRevResearch.2.043320

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Published by the American Physical Society