https://doi.org/10.1140/epjc/s10052-016-4567-x
Regular Article - Theoretical Physics
Do nuclear collisions create a locally equilibrated quark–gluon plasma?
1
Department of Physics, University of Colorado at Boulder, 390 UCB, Boulder, CO, 80309, USA
2
Center for Theory of Quantum Matter, University of Colorado, Boulder, CO, 80309, USA
* e-mail: paul.romatschke@colorado.edu
Received:
12
October
2016
Accepted:
7
December
2016
Published online:
10
January
2017
Experimental results on azimuthal correlations in high energy nuclear collisions (nucleus–nucleus, proton–nucleus, and proton–proton) seem to be well described by viscous hydrodynamics. It is often argued that this agreement implies either local thermal equilibrium or at least local isotropy. In this note, I present arguments why this is not the case. Neither local near-equilibrium nor near-isotropy are required in order for hydrodynamics to offer a successful and accurate description of experimental results. However, I predict the breakdown of hydrodynamics at momenta of order seven times the temperature, corresponding to a smallest possible QCD liquid drop size of 0.15 fm.
© The Author(s), 2017
