PERTURBATIVE AND NONPERTURBATIVE QUARKS AND GLUONS

BRST invariance supplies a sufficient condition for the observability of fields. We show that there is a global obstruction to the observabi lity of quarks and gluons and argue that they will not become observab les at finite temperature. We give expressions for quarks and gluons t hat are, however, perturbatively BRST invariant, and hence locally obs ervable, up to order g2 and g respectively.