The authors then remarked that a "gently changing logarithmic slope" for a density profile function could also accommodate approximately flat rotation curves over large scales. They found the famous Navarro–Frenk–White profile, which is consistent both with N-body simulations and observations given by ρ ρ ( r ) = ρ ρ 0 r R s ( 1 + r R s ) 2 where the central density, ρ 0, and the scale radius, R s, are parameters that vary from halo to halo. Because the slope of the density profile diverges at the center, other alternative profiles have been proposed, for example the Einasto profile, which has exhibited better agreement with certain dark matter halo simulations.