Applications of QCD sum rules at finite temperature

QCD sum-rule techniques are applied to the spectra of and J̌ mesons at finite temperature to investigate the relative importance of quark and gluon condensates and perturbative thermal effects in determining bound-state parameters. Of particular interest are the consequences of nonperturbative physics persisting above the deconfinement phase transition, which is implied by nonzero gluon condensates found in lattice calculations. For the meson, the quark thermal bath induces only a smooth variation in the hadronic parameters as the temperature is increased; the quark condensate and its temperature dependence are the most important factors. For the J̌ meson, perturbative thermal effects overwhelm the gluon condensate contribution at a temperature around 100 MeV, so that high-temperature charmonium physics is consistent with that expected in a weakly interacting quark-gluon plasma. Corrections to other plasma properties from nonperturbative physics are discussed.