  The stability of the chromomagnetic Savvidy vacuum in QCD under the influence
of positive Riemannian curvature is studied. The heat traces of the operators
relevant to SO(2) gauge-invariant Yang-Mills fields and Faddeev-Popov ghosts
are calculated on product spaces of S^2 and S^1 \times S^1. It is shown that
the chromomagnetic vacuum with covariantly constant chromomagnetic field is
stable in a certain set of radii and field strengths.
