Debye mass at the QCD transition in the PNJL model
We consider colour-electric screening as expressed by the quark contribution
to the Debye mass calculated in a PNJL model with emphasis on confining and
chiral symmetry breaking effects. We observe that the screening mass is
entirely determined by the nonperturbative quark distribution function and
temperature dependent QCD running coupling. The role of the gluon background
(Polyakov loop) is to provide strong suppression of the number of charge
carriers below the transition temperature, as an effect of confinement, while
the temperature dependent dynamical quark mass contributes additional
suppression, as an effect of chiral symmetry breaking. An alternative
derivation of this result from a modified kinetic theory is given, which allows
for a slight generalization and explicit contact with perturbative QCD. This
gives the possibility to gain insights into the colour screening mechanism in
the region near the QCD pseudocritical temperature and to provide a guideline
for the interpretation of lattice QCD data.