Semi-infinite systems are considered which give rise to a delocalization transition of the interface between two coexisting phases. Since the interface position becomes a zero mode at the transition, interface fluctuations invalidate mean-field theory for space dimension d<~3. An effective field-theoretic model for this zero mode is obtained via the collective-coordinate method. Results for a simplified version of this model in d=2 and in d=3 are reported.
Lipowsky et al. (Fri,) studied this question.