Percolation approach to Quark Gluon Plasma and $J/\psi$ suppression
  It is shown that the critical threshold for percolation of the overlapping strings exchanged in heavy ion collisions can naturally explain the sharp strong suppresion of $J/\psi$ shown by the experimental data on central Pb--Pb collisions, which does not occur in central O--U and S--U collisions. 
N. Armesto, M. A. Braun, E. G. Ferreiro and C. Pajares