Abstract
Surfactant molecules form an adsorbed monolayer on the surface of water. It is possible that the adsorbed monolayer has both an ordered state and a disordered state of molecules. As a consequence, a phase transition is expected to occur between these two states. It is also expected than an interaction between the molecules is described by the well-known XY model. We study numerically an internal phase transition of the adsorbed monolayer by using XY model defined on triangulated surfaces. We find that the shape fluctuation of surfaces strengthen the internal phase transition of the model.
