  Within the constrained Hartree-Fock (CHF) theory, an analytic condition is
derived to estimate whether a concept of the self-consistent mean field is
realized or not in level repulsive region. The derived condition states that an
iterative calculation of CHF equation does not converge when the quantum
fluctuations coming from two-body residual interaction and quadrupole
deformation become larger than a single-particle energy difference between two
avoided crossing orbits. By means of the numerical calculation, it is shown
that the analytic condition works well for a realistic case.
