  High derivative terms do not play a major role in field theories because of
the associated complexity and inherent difficulty in connecting these terms to
physically measurable quantities. A role for higher derivative terms is
analyzed for the case of field theories used to describe phase separated
systems. In these theories, higher derivative terms are directly connected to
an interfacial free energy which contains the mean and the Gaussian curvature
and are shown to determine explicitly the shape of the interface.
