  We investigate a radiative electroweak gauge symmetry breaking scenario via
the Coleman-Weinberg mechanism starting from a completely flat Higgs potential
at the Planck scale ("flatland scenario"). In our previous paper, we showed
that the flatland scenario is possible only when an inequality K<1 among the
coefficients of the beta functions is satisfied. In this paper, we calculate
the number K in various models with an extra U(1) gauge sector in addition to
the SM particles. We also show the renormalization group (RG) behaviors of a
couple of the models as examples.
