  A Rayleigh-Schrodinger type of perturbation scheme is employed to study weak
self-interacting scalar potential perturbations occurring in scalar field
models describing 1D domain kinks and 3D domain walls. The solutions for the
unperturbed defects are modified by the perturbing potentials. An illustration
is provided by adding a cubic potential to the familiar quartic kink potential
and solving for the first order correction to the kink solution, using a "slab
approximation". A result is the appearance of an asymmetric scalar potential
with different, nondegenerate, vacuum values and the subsequent formation of
vacuum bubbles.
