2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55610The asymptotic behaviour of the vacuum energy density, ${\bar E}(θ)$, at $θ\ra \pm i \infty$ is found out. A new interpretation and a qualitative discussion of the ${\bar E}(θ)$ behaviour are presented. It is emphasized that the vacuum is doubly degenerate at $θ=π$, and the quark electric string can terminate on the domain wall interpolating between these two vacua. The potential of the monopole field condensing in the Yang-Mills vacuum is obtained.17 pages, Latex, no figures; additional explanations are given in sects.1 and 3; the final versionHigh Energy Physics - TheoryHigh Energy Physics - Phenomenologytext