  The vacuum two-point function is calculated beyond the Gaussian approximation
during the second order phase transition. It is found that the correlation
function is dominated by the Gaussian term immediately after the phase
transition but later is taken over by non-Gaussian terms as the spinodal
instability continues. The non-Gaussian effects lead to larger size of domains
and may imply a smaller density of topological defects than that predicted by
the Hartree-Fock approximation.
