EFFECTIVE POTENTIAL FOR A COVARIANTLY CONSTANT GAUGE FIELD IN CURVED SPACETIME

We discuss the influence of gravitational effects on the stabilization of the chromomagnetic vacuum. The one-loop effective potential for a covariantly constant SU(2) gauge field in S-2 x R(2) and T-2 x R(2) is calculated. The possibility of curvature-induced phase transitions be tween zero and nonzero chromomagnetic vacua is found-which is also con firmed through the calculation of the renormalization-group-improved e ffective potential on constant-curvature spaces with small curvature. Numerical evaluation indicates that for some curvatures the imaginary part of the effective potential disappears (gravitational stabilizatio n of the chromomagnetic vacuum occurs).