SHAPE TRANSFORMATIONS OF DOMAINS IN MIXED-FLUID FILMS AND BILAYER-MEMBRANES

We study the stability and shapes of domains in mixed-fluid films and membranes. These domains can result from the inclusion of an impurity in a fluid membrane, or from phase separation within the membrane. We show that for small but finite line and surface tensions and for finit e spontaneous curvatures, an equilibrium phase of protruding circular domains is obtained at low impurity concentrations. However, at higher concentrations we predict a transition from circular domains to strip es. In both cases, we calculate the shapes of these domains within the Monge representation for the membrane shape.