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SUMMARY:Equilibration in finite gluon systems
DTSTART;VALUE=DATE-TIME:20180515T171000Z
DTEND;VALUE=DATE-TIME:20180515T174000Z
DTSTAMP;VALUE=DATE-TIME:20210127T082231Z
UID:indico-contribution-2883181@indico.cern.ch
DESCRIPTION:Speakers: Georg Wolschin (Heidelberg University)\nThe equilibr
ation of a finite Bose system is modelled using a gradient expansion of th
e collision integral in the bosonic Boltzmann equation that leads to a non
linear transport equation. Employing a method that had been proposed earli
er for the analytical solution of the equilibration problem in a finite fe
rmion system [1]\, the basic equation for bosons and in particular\, gluon
s\, is solved in closed form for constant transport coefficients through a
nonlinear transformation.\n\nWith initial conditions that are appropriate
for the gluon system in a relativistic heavy-ion collision such as Au+Au
or Pb+Pb at energies reached at RHIC or LHC\, the exact solution is derive
d. It agrees well with the numerical solution of the nonlinear equation. T
he analytical expression for the local equilibration time in the thermal t
ail is compared to the corresponding case for fermions. The method is also
applicable to the (nonrelativistic) equilibration of a cold quantum gas.\
n\nDue to the nonlinearity of the basic equation\, the sharp edges of the
initial gluon distribution at Q_s â‰ˆ 1 GeV are continously smeared out an
d local equilibrium of the gluon distribution with a thermal tail in the u
ltraviolett region is rapidly attained [2]. Although gluon condensate form
ation at p=0 is in principle possible\, due to inelastic processes and the
nonconservation of particle number in relativistic collisions this appear
s unlikely to occur in heavy-ion collisions.\n\nThe thermal equilibration
time for gluons turns out to be nine times shorter than the equilibration
time for fermions (quarks) as a consequence of the statistical properties
of bosons versus fermions [2]. This result can be viewed as one of the mai
n reasons for the very short local equilibration time in relativistic heav
y-ion collisions that are dominated by gluons in their initial stage.\n\n\
n[1] G. Wolschin\, Phys. Rev. Lett. 48\, 1004 (1982).\n[2] G. Wolschin\, s
ubmitted to Physica A (2017)\; arXiv:1712.02659.\n\nhttps://indico.cern.ch
/event/656452/contributions/2883181/
LOCATION:Palazzo del CasinĂ² First floor and third floor
URL:https://indico.cern.ch/event/656452/contributions/2883181/
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