Topological instabilities of spherical vesicles
  Within the framework of the Helfrich elastic theory of membranes and of differential geometry we study the possible instabilities of spherical vesicles towards double bubbles. We find that not only temperature, but also magnetic fields can induce topological transformations between spherical vesicles and double bubbles and provide a phase diagram for the equilibrium shapes. 
O.V. Manyuhina, A. Fasolino, P.C.M. Christianen and M.I. Katsnelson