GAUGE-INVARIANT TREATMENT OF THE ELECTROWEAK PHASE-TRANSITION

We evaluate the gauge invariant effective potential for the composite field sigma = 2PHI(dagger)PHI in the SU(2)-Higgs model at finite tempe rature. Symmetric and broken phases correspond to the domains sigma le ss-than-or-equal-to /3 and sigma > T2/3, respectively. The effective p otential increases very steeply at small values of sigma. Predictions for several observables, derived from the ordinary and the gauge invar iant effective potential, are compared. Good agreement is found for th e critical temperature and the jump in the order parameter. The result s for the latent heat differ significantly for large Higgs masses.