  We study the RHIC data on long range rapidity correlations, comparing their
main trends with different string model simulations. Particular attention is
paid to color percolation model and its similarities with color glass
condensate. As both approaches corresponds, at high density, to a similar
physical picture, both of them give rise to a similar behavior on the energy
and the centrality of the main observables. Color percolation explains the
transition from low density to high density.
