field depends on the distribution of the transverse vector potential it is necessary to know the wave functional of the system. A self-consistent variational ansatz can be chosen in a Gaussian form,

$$\Psi[A] = \exp\left( - \frac{1}{2}
 \int {\frac{d\p}{(2\pi)^3}} \omega(p)
  \A^a(\p)\cdot \A^a(-\p) \right). \label{varia}$$

The parameter $\omega(p)$ ($p\equiv |\p|$) is determined by minimizing the expectation value of the energy density of the vacuum ([*i.e.*]{} without sources). The boundary condition referred to above corresponds to setting $\omega(0) \equiv \mu$ to be finite, which plays the role of $\Lambda_{QCD}$, [*i.e*]{} it controls the position of the Landau pole. Minimizing the energy density of the vacuum leads to a set of coupled self-consistent integral equations: one for $\omega$, one for the expectation value of the inverse of the FP operator, $d(p)$, $$\begin{gathered}
(2\pi)^3 \delta(\p-\q)\delta_{ab} d(p)
 \equiv \\
 \int d\x d\y e^{-i\p\cdot\x} e^{i\q\cdot\y} 
 \langle \Psi| \left[ \frac{g}{1 - \lambda}\right]^{ab}_{\x,\y}
 |\Psi \rangle / {\langle \Psi|\Psi \rangle },
\label{d}\end{gathered}$$ and one for the expectation value of the square of the inverse of the FP operator, which appears in the matrix elements of $V_C$, $$\begin{gathered}
(2\pi)^3 \delta(\k-\q)\delta_{ab} f(p)d^2(p) 
 \equiv \\
 \int d\x d\y e^{-i\p\cdot\x} e^{i\q\cdot\y} 
 \langle \Psi| \left[ \left(\frac{g}{1 - \lambda}\right)^2
 \right]^{ab}_{\x,\y}
 |\Psi \rangle / {\langle \Psi|\Psi 