On the stability of center vortices and the gyromagnetic ratio of quantum fluctuations in Yang-Mills theory

The importance of center vortices for the understanding of the confining properties of SU(N) Yang-Mills theories is well established in the lattice. However, in the continuum, there is a problem concerning the relevance of center vortex background fields. They display the so called Savvidy-Nielsen-Olesen instability, associated with a gyromagnetic ratio g^(b)_m=2 for the off-diagonal gluons. In this work, we discuss fluctuations around an alternative manner to introduce thin center vortices, namely, as defects of a local color frame. In particular, we point out that the coupling of these fluctuations with defects occurs with gyromagnetic ratio g^(d)_m=1. As a consequence, the analysis of stability is completely modified, as g_m=1 is known to be a critical value that dictates the general properties of the spectrum of Schr\"odinger operators. In particular, thin center vortex defects turn out to be stable objects.