  We calculate the four-dimensional low-energy effective action for the
perturbations of a two-scalar domain wall model in five dimensions. Comparison
of the effective action to the Nambu-Goto action reveals the presence of an
additional coupling between the light scalar field and the massless translation
mode (branon excitation), which can be written in terms of the curvature scalar
of the induced metric. We comment on the impact of this interaction to branon
physics.
