Halo bias b_h as a function of mass local density in cubical volumes with side length l = 26 h^-1 Mpc (red), l = 14 h^-1 Mpc (black) and l = 6 h^-1 Mpc (blue), which have the same volume as a sphere of radius R = 3.72,8.68 and 16.13 h^-1 Mpc, respectively. The corresponding dashed line shows a simple prediction where is the linear density corresponding to (according to the spherical collapse model) and is the linear variance at Lagrangian scale .