Carsten Greiner

Transport coefficients of hadronic matter near Tc.

A hadron resonance gas model including all known particles and resonances with masses m < 2 GeV and an exponentially rising density of Hagedorn states for m > 2 GeV is used to obtain an upper bound on the shear viscosity to entropy density ratio, eta/s approximately 1/(4pi), of hadronic matter near Tc. We found a large trace anomaly and small speed of sound near Tc, which agree well with recent lattice calculations. We comment on the bulk viscosity to entropy density ratio close to Tc.

Open heavy flavor in Pb+Pb collisions at √ s=2.76 TeV within a transport model

The space-time evolution of open heavy flavor is studied in Pb+Pb collisions at √ s=2.76 TeV using the partonic transport model Boltzmann Approach to MultiParton Scatterings (BAMPS). An updated version of BAMPS is presented which allows interactions among all partons: gluons, light quarks and heavy quarks. Heavy quarks, in particular, interact with the rest of the medium via binary scatterings with a running coupling and a Debye screening which is matched by comparing to hard thermal loop calculations. The lack of radiative processes in the heavy flavor sector is accounted for by scaling the binary cross section with a phenomenological factor K = 3.5, which describes well the elliptic flow v2 and nuclear modification factor RAA at RHIC. Within this framework we calculate in a comprehensive study the v2 and RAA of all interesting open heavy flavor particles at the LHC: electrons, muons, D mesons, and non-prompt J/ψ from B mesons. We compare to experimental data, where it is already available, or make predictions. To do this accurately next-to-leading order initial heavy quark distributions are employed which agree well with proton-proton data of heavy flavor at √ s=7 TeV.

PQCD calculations of elliptic flow and shear viscosity at RHIC

The elliptic flow v_{2} and the ratio of the shear viscosity over the entropy density, eta/s, of gluon matter are calculated from the perturbative QCD (pQCD) based parton cascade Boltzmann approach of multiparton scatterings. For Au+Au collisions at sqrt[s]=200A GeV the gluon plasma generates large v_{2} values measured at the BNL Relativistic Heavy Ion Collider. Standard pQCD yields eta/s approximately 0.08-0.15 as small as the lower bound found from the anti-de Sitter/conformal field theory conjecture.

Elliptic flow and energy loss of heavy quarks in ultrarelativistic heavy ion collisions

the modifications we employed to the standard leading order cross section. In Sec. IV we show our results for RHIC and LHC and compare them to the experimental data where possible. Finally, we conclude with a short summary.

Quark phases in neutron stars and a third family of compact stars as signature for phase transitions

Abstract The appearance of quark phases in the dense interior of neutron stars provides one possibility to soften the equation of state (EOS) of neutron star matter at high densities. This softening leads to more compact equilibrium configurations of neutron stars compared to pure hadronic stars of the same mass. We investigate the question to which amount the compactness of a neutron star can be attributed to the presence of a quark phase. For this purpose we employ several hadronic EOS in the framework of the relativistic mean-field (RMF) model and an extended MIT bag model to describe the quark phase. We find that — almost independent of the model parameters — the radius of a pure hadronic neutron star gets typically reduced by 20–30% if a pure quark phase in the center of the star does exist. For some EOS we furthermore find the possibility of a third family of compact stars which may exist besides the two known families of white dwarfs and neutron stars. We show how an experimental proof of the existence of a third family by mass and radius measurements may provide a unique signature for a phase transition inside neutron stars.

Shear Viscosity in a Gluon Gas

The relation of the shear viscosity coefficient to the recently introduced transport rate is derived within relativistic kinetic theory. We calculate the shear viscosity over entropy ratio eta/s for a gluon gas, which involves elastic gg-->gg perturbative QCD (PQCD) scatterings as well as inelastic gg<-->ggg PQCD bremsstrahlung. For alpha_{s}=0.3 we find eta/s=0.13 and for alpha_{s}=0.6, eta/s=0.076. The small eta/s values, which suggest strongly coupled systems, are due to the gluon bremsstrahlung incorporated.

Jet quenching and elliptic flow at the RHIC and the LHC within a pQCD-based partonic transport model

The description of jet quenching and elliptic flow at the RHIC and the LHC within a common dynamical framework has been notoriously difficult. In this paper, an approach using the perturbative QCD-based partonic transport model BAMPS (Boltzmann approach to multi-parton scatterings) is presented that has recently been extended to include light quarks. The investigations are complemented by a study on the suppression of D-mesons at the LHC based on elastic interactions with the medium.

Third-order relativistic dissipative hydrodynamics

Following the procedure introduced by Israel and Stewart, we expand the entropy current up to the third order in the shear stress tensor

Relativistic shock waves in viscous gluon matter.

\pi^{\alpha\beta}

Elliptic flow of gluon matter in ultrarelativistic heavy-ion collisions

and derive a novel third-order evolution equation for