We review progress towards solving
the problem of thermalization in heavy ion collisions and discuss
surprising recent numerical results-in particular the discovery of a
non-thermal fixed point (typical of weak wave turbulence) in an
expanding non-Abelian plasma [1]. Remarkably the self-similar behavior
of this fluid is identical to those of over-occupied N component
self-interacting scalar theories that model, for instance, the
behavior of cold atomic gases [2]. We discuss possible insights into
the hottest fluids produced on earth obtained from the coldest
fluids--in particular, the possible formation of transient
Bose-Einstein condensates. We address, in this context, some of
the challenges post by the numerical results to kinetic descriptions
[3]. If time permits, we will outline progress on related fronts: i)
how recent "ridge" correlations measured in small systems impact
our understanding of the thermalization process [4], and ii) a
nonperturbative computation of the off-equilibrium sphaleron
transition rate [5].
References:
[1] J. Berges, K.
Boguslavski, S. Schlichting and R. Venugopalan, Turbulent
thermalization process in heavy-ion collisions at
ultrarelativistic energies, Phys.
Rev. D 89, 074011 (2014).
[2] J. Berges,
K. Boguslavski, S. Schlichting and R. Venugopalan, Universality far
from equilibrium: From superfluid Bose gases to heavy-ion
collisions, Phys.
Rev. Lett. 114, 061601
(2015)
[3] ibid., arXiv: 1508.03073 [hep-ph], to appear in
PRD.
[4] B. Schenke
and R. Venugopalan,
Collective effects in lightâheavy ion collisions, Nucl. Phys. A 931, 1039 (2014); T. Lappi,
B. Schenke, S. Schlichting and R. Venugopalan, Tracing the origin
of azimuthal gluon correlations in the color glass condensate, arXiv:1509.03499
[hep-ph].
[5]
M. Mace, S. Schlichting, and R. Venugopalan, to appear.
Nuclear
Physics Colloquium