Speaker
Dr
Marcus Bluhm
(Laboratoire SUBATECH)
Description
The knowledge of transport coefficients of the Quark-Gluon Plasma
(QGP) gives fundamental insights into the nature of strongly
interacting matter under extreme conditions. By means of
relativistic heavy-ion collisions, these properties are intended
to be experimentally revealed, providing also information about
the structure of the produced hot matter. One of the remarkable
findings is that the QGP created in experiments at RHIC and LHC
is an almost ideal fluid obeying, apart from ultra-cold fermionic
systems near unitarity, the smallest shear viscosity to entropy
density ratio observed in nature.
By means of a quasi-particle model for QCD thermodynamics, which
is related to QCD via the two-loop phi-functional formalism,
featuring dynamically generated self-energies of the excitation
modes and being extended to non-equilibrium systems
self-consistently within an effective kinetic theory approach,
the temperature dependence of shear and bulk viscosity
coefficients of the QGP is investigated [1]. Showing the
parametric dependencies on coupling and temperature known from
perturbative QCD at large temperatures, their extrapolation into
the non-perturbative regime near the deconfinement transition
temperature exhibits fairly nice agreement with available lattice
QCD results for the pure gluon plasma. Moreover, the ratio of bulk
to shear viscosity depicts at large temperatures the quadratic
dependence on the conformality measure known from perturbative
QCD, while in the vicinity of the deconfinement transition a
linear behaviour as known from specific strongly coupled theories
based on the gauge/string duality is found [2]. Via weak coupling
arguments, an interrelation between the specific shear viscosity
and the energy loss parameter can be derived [3]. The transport
coefficient determined in this way exhibits a pronounced
temperature dependence, which serves as a possible explanation
for the observed centrality dependence of the azimuthal
anisotropic flow.
[1] M. Bluhm, B. Kampfer, K. Redlich, Phys. Rev. C 84 (2011) 025201
[2] M. Bluhm, B. Kampfer, K. Redlich, Phys. Lett. B 709 (2012) 77
[3] A. Majumder, B. Muller, X.-N. Wang, Phys. Rev. Lett. 99 (2007)
192301
Author
Dr
Marcus Bluhm
(Laboratoire SUBATECH)
Co-authors
Prof.
Burkhard Kampfer
(Helmholtzzentrum Dresden-Rossendorf)
Prof.
Krzysztof Redlich
(University of Wroclaw)
Dr
Marlene Nahrgang
(Laboratoire SUBATECH)
