Center-vortex solutions of the Yang-Mills effective action in three and four dimensions

We calculate the one-loop effective action of the SU(2) Yang-Mills theory for center-vortex configurations, both in 3D and 4D. We find that in both cases there are minima of the effective action, corresponding to vortices of the transverse size approximately 4/g₃² and 1.7/Λ_MS, respectively. The values of the effective actions at the minima are negative, suggesting that the Euclidian vacuum may be unstable with respect to the creation of vortices.