Energy and pressure densities of a hot quark-gluon plasma

We calculate the energy and hydrostatic pressure densities of a hot quark-gluon plasma in thermal equilibrium through diagrammatic analyses of the statistical average, $langle Theta_{mu u} rangle$, of the energy-momentum-tensor operator $Theta_{mu u}$. To leading order at high temperature, the energy density of the long wave length modes is consistently extracted by applying the hard-thermal-loop resummation scheme to the operator-inserted no-leg thermal amplitudes $langle Theta_{mu u} rangle$. We find that, for the long wave length gluons, the energy density, being positive, is tremendously enhanced as compared to the noninteracting case, while, for the quarks, no noticeable deviation from the noninteracting case is found.