 Mass-concentration relation of dark-matter haloes

The mass-concentration relation of dark-matter haloes describes a statistical trend of halo concentration with mass and epoch. The original Navarro--Frenk--White profile simulations connected denser inner structure with earlier assembly, helping explain why smaller halos were typically more concentrated in those hierarchical models. The relation has scatter and depends on the cosmology and halo definition; it is not a unique concentration fixed by mass alone.^[ref]