The model of a domain wall ("thick brane") in noncompact five-dimensional space-time is considered
with geometries of AdS type generated by self-interacting scalar matter composed of two
fields with minimal coupling to gravity. The mixing of scalar and gravitational degrees of freedom
leads to contributions to the invariant scalar fluctuations potential that remain nontrivial in
the limit of turned off gravity. This leads to the disappearance of the Goldstone mode associated
with translational symmetry breaking and to the different mass of the Higgs-like scalar state.