Bifurcation and fine structure phenomena in critical collapse of a   self-gravitating $\sigma$-field
  Building on previous work on the critical behavior in gravitational collapse of the self-gravitating SU(2) $\sigma$-field and using high precision numerical methods we uncover a fine structure hidden in a narrow window of parameter space. We argue that this numerical finding has a natural explanation within a dynamical system framework of critical collapse. 
Peter C. Aichelburg, Piotr Bizon and Zbislaw Tabor