Structure of exotic three-body systems
  The classification of large halos formed by two identical particles and a core is systematically addressed according to interparticle distances. The root-mean-square distances between the constituents are described by universal scaling functions obtained from a renormalized zero-range model. Applications for halo nuclei, $^{11}$Li and $^{14}$Be, and for atomic $^4$He$_3$ are briefly discussed. The generalization to four-body systems is proposed. 
T. Frederico, M.T. Yamashita, A. Delfino and Lauro Tomio