QCD collisional energy loss reexamined.

It is shown that at a large temperature and E --> infinity the QCD collisional energy loss reads dE/dx approximately alpha(m(D)2)T2. Compared to previous approaches, which led to dE(B)/dx approximately alpha2 T2 ln(ET/m(D)2) similar to the Bethe-Bloch formula in QED, we take into account the running of the strong coupling. As one significant consequence, due to asymptotic freedom, dE/dx becomes E independent for large parton energies.

The hot nonperturbative gluon plasma is an almost ideal colored liquid.

We study properties of a gluon plasma above the critical temperature Tc in a generalized quasiparticle approach with a Lorentz spectral function. The model parameters are determined by a fit of the entropy s to lattice QCD data. The effective degrees of freedom are found to be rather heavy and of a sizable width.

Quark dispersion relation and dilepton production in the quark-gluon plasma.

Under very general assumptions we show that the quark dispersion relation in the quark-gluon plasma is given by two collective branches, of which one has a minimum at a nonvanishing momentum. This general feature of the quark dispersion relation leads to structures (van Hove singularities, gaps) in the low mass dilepton production rate, which might provide a unique signature for the quark-gluon plasma formation in relativistic heavy ion collisions.