  We derive the Polyakov-loop thermodynamic potential in the perturbative
approach to pure SU(3) Yang-Mills theory. The potential expressed in terms of
the Polyakov loop in the fundamental representation corresponds to that of the
strong-coupling expansion, of which the relevant coefficients of the gluon
energy distribution are specified by characters of the SU(3) group. At high
temperatures the derived gluon potential exhibits the correct asymptotic
behavior, whereas at low temperatures, it disfavors gluons as appropriate
dynamical degrees of freedom. In order to quantify the Yang-Mills
thermodynamics in a confined phase, we propose a hybrid approach which matches
the effective gluon potential to the one of glueballs constrained by the QCD
trace anomaly in terms of a dilaton. We also discuss the interplay between the
chromomagnetic and chromoelectric gluon dynamics.
