Lagrangian of the form $$\begin{aligned}
    \mathcal{L}_{\mathrm{eff}} &=& - \frac{1}{4\Lambda^2}\left(D^{ab}_\nu F^b_{\rho\mu} D^{ac}_\nu F^c_{\rho\mu} + D^{ab}_\mu F^b_{\mu\nu} D^{ac}_\rho F^c_{\rho\nu }\right)  
    \nonumber\\
    &-&U_{\mathrm{eff}}   
    \nonumber \\
U_{\mathrm{eff}}&=&\frac{\Lambda^4}{12} {\rm Tr}\left(C_1\breve{ f}^2 + \frac{4}{3}C_2\breve{ f}^4 - \frac{16}{9}C_3\breve{ f}^6\right),
\label{ueff}\end{aligned}$$ where $\Lambda$ is a scale of QCD related to gluon condensate, $\breve f=\breve F/\Lambda^2$, and $$\begin{aligned}
 && D^{ab}_\mu = \delta^{ab} \partial_\mu - i\breve{ A}^{ab}_\mu = \partial_\mu - iA^c_\mu {(T^c)^{ab}},
\\
 && F^a_{\mu\nu} = \partial_\mu A^a_\nu - \partial_\nu A^a_\mu - if^{abc} A^b_\mu A^c_\nu,
\\
 && \breve{ F}_{\mu\nu} = F^a_{\mu\nu} T^a,\ \ \ T^a_{bc} = -if^{abc}
\\
 && {\rm Tr}\left(\breve{ F}^2\right) = \breve{ F}^{ab}_{\mu\nu}\breve{ F}^{ba}_{\nu\mu} = -3 F^a_{\mu\nu}F^a_{\mu\nu} \leq 0,
\\ && C_1>0, \ C_2>0, \ C_3 > 0.\end{aligned}$$ Detailed discussion of this expression can be found in [@NG2011]. Here it should be noted that all symmetries of QCD are respected and the signs of the constants are chosen so that the action is bounded from below and its minimum corresponds to the fields with nonzero strength, i.e. $F^2\not=0$ at the minimum. Thus, an important input is the existence of the nonzero gluon condensate. By inspection, one gets as an output twelve (for $SU(3)$) global degenerate discrete minima. The minima are achieved for covariantly constant Abelian (anti-)self-dual fields $$\begin{aligned}
