Drumhead model

Starting point is the description of the interface in terms of the drumhead model [273], i.e. we disregard for the moment the fact that the interface has a non-trivial intrinsic profile with width w0, and treat it like a sharp kink in terms of the local interfacial height h(x,y) only, x,y being coordinates along the lower surface (at z=0). Then the effective free energy functional Heff [h] associated with interfacial fluctuations can be written as [220]... 

This coarse-graining can also be used to justify the "drumhead model of an interface, cf. fig. 6, where on a more macroscopic scale the internal structure of the interface is disregarded, and one is more interested in large scale fluctuations of the local position z = h(x,y) of this interface. In this sharp kink approximation the interface is described similarly to an elastically deformable membrane. 

---