Nearly spherical vesicles: Shape fluctuations

Isolated vesicles with ''insufficient'' area have a finite surface tension and spherical shapes, whereas vesicles with ''excess'' area are necessarily aspherical. We consider the crossover behavior between both kinds of vesicles occurring as the equilibrium area increases. In the mean field approximation it is a second-order phase transition from the spherical to aspherical shape. We demonstrate the fluctuations smear the transition. The critical behavior of the amplitudes of fluctuations and of their characteristic times is investigated. (C) 1996 American Institute of Physics.