“…[5], and also found on the lattice [39], non-oriented center vortices are absolutely necessary for a non-vanishing Pontryagin index. Furthermore, in 4d ensembles of percolating center vortices, the coexistence of oriented and non-oriented components, N -matching rules among center-vortex surfaces, and natural matching rules among monopole lines, is essential to generate a confining flux tube [9] (see also [10]). Indeed, the center-vortex field configurations in our vacuum wave functional incorporate all the features and correlations of center vortices observed for SU (2) in the indirect maximal center gauge, naturally extended to SU (N ).…”