  The problem of existence of a stable vacuum field in a pure quantum
chromodynamics (QCD) is revised. Our approach is based on using classical
stationary non-linear wave type solutions with intrinsic mass scale parameter.
Such solutions can be treated as quantum mechanical wave functions describing
massive spinless states in quantum theory. We verify whether non-linear wave
type solutions can form a stable vacuum field background within the framework
of effective action formalism. We demonstrate that there is a special class of
stationary generalized Wu-Yang monopole solutions which are stable against
quantum gluon fluctuations.
