Abstract
An off-lattice model of a vesicle assembly in two dimensions is studied by use of computer simulation techniques. The vesicles are represented as closed, self-avoiding tethered chains with bending rigidity. We present studies for a system of fluctuating vesicle configurations, where the total number of monomers is fixed, but the vesicle size distribution may vary, i.e. the vesicles can fuse or break up. The phase diagram obtained in the case of zero osmotic pressure contains a vesicle phase with broken in-out symmetry and a symmetric "bicontinuous" phase. The phases are separated by a line of Ising-type second-order phase transitions, and the functional form of the phase boundary is derived from simple scaling arguments.