Dynamical quasiparticles properties and effective interactions in the sQGP

Dynamical quasiparticle properties are determined from lattice QCD along the line of the Peshier model for the running strong coupling constant in case of three light flavors. By separating time-like and space-like quantities in the number density and energy density the effective degrees of freedom in the gluon and quark sector may be specified from the time-like densities. The space-like parts of the energy densities are identified with interaction energy (or potential energy) densities. By using the time-like parton densities (or scalar densities) as independent degrees of freedom—instead of the temperature T and chemical potential μq as Lagrange parameters—variations of the potential energy densities with respect to the time-like gluon and/or fermion densities lead to effective mean-fields for time-like gluons and quarks as well as to effective gluon–gluon, quark–gluon and quark–quark (quark–antiquark) interactions. The latter dynamical quantities are found to be approximately independent on the quark chemical potential μq and thus well suited for an implementation in off-shell parton transport approaches. Results from the dynamical quasiparticle model (DQPM) in case of two dynamical light quark flavors are compared to lattice QCD calculations for the net quark density ρq(T,μq) as well as for the ‘back-to-back’ differential dilepton production rate by annihilation. The DQPM is found to pass the independent tests.