Correlations in IInterfaces with Surfactants

The existence or nonexistence of the bending coefficient in liquid iInterfaces, as well as the applicability of the Helfrich free energy, is examined by comparing correlations in the iInterfaces with or without a weak surfactant. In the latter case, the formation of a bilayer is studied and density density correlations and height height correlations are reported, analyzed, and compared with ``normalʹʹ liquid iInterfaces. In particular, the role of lateral tension is discussed.