On Zero-Mass Bound States in Super-Membrane Models
  For the simplest case of a supermembrane matrix model, various symmetry reductions are given, with the fermionic contribution(s) (to an effective Schr\"odinger equation) corresponding to an attractive $\delta$-function potential (towards zero-area configurations). The differential equations are real, and are shown not to admit square-integrable real solutions (even when allowing non-vanishing boundary conditions at infinity). Complex solutions, however, are not excluded by this argument. 
Jens Hoppe