I compare the density profile of dark matter ( DM ) halos in cold dark matter ( CDM ) N-body simulations with 1 h ^ { -1 } Mpc , 32 h ^ { -1 } Mpc , 256 h ^ { -1 } Mpc and 1024 h ^ { -1 } Mpc box sizes .
I compare the profiles when the most massive halos are composed of about 10 ^ { 5 } DM particles .
The DM density profiles of the halos in the 1 h ^ { -1 } Mpc box at redshift z \sim 10 show systematically shallower cores with respect to the corresponding halos in the 32 h ^ { -1 } Mpc simulation at z \sim 3 that have masses , M _ { dm } , typical of the Milky Way and are fitted by a NFW profile .
The DM density profiles of the halos in the 256 h ^ { -1 } Mpc box at z \sim 0 are consistent with having steeper cores than the corresponding halos in the 32 h ^ { -1 } Mpc simulation , but higher mass resolution simulations are needed to strengthen this result .
Combined , these results suggest that the density profile of DM halos is not universal , presenting shallower cores in dwarf galaxies and steeper cores in clusters .
More work is needed to validate this finding at z = 0 .
Physically the result sustains the hypothesis that the mass function of the accreting satellites determines the inner slope of the DM profile .
But the result can also be interpreted as a trend with the dynamical state in the assembly process of halos of different mass .
In comoving coordinates , r , the profile

\rho _ { dm } \propto { 1 \over X ^ { \alpha } ( 1 + X ) ^ { 3 - \alpha } } with X = c _ { \Delta } r / r _ { \Delta } and \alpha = ( 9 + 3 n ) / ( 5 + n ) \approx 1.3 + ( M _ { dm, 14 } ^ { 1 / 6 } -1 ) / ( M _ { dm, 14 } ^ { 1 / 6 } +1 ) , provides a good fit to all the DM halos from dwarf galaxies to clusters at any redshift with the same concentration parameter c _ { \Delta } \sim 7 .
Here , r _ { \Delta } ( M _ { dm } ) is the virial radius , n is the effective spectral index of the initial power spectrum of density perturbations and M _ { dm, 14 } = M _ { dm } / ( 3 \times 10 ^ { 14 } M _ { \odot } ) .
The slope , \gamma , of the outer parts of the halo appears to depend on the acceleration of the universe : when the scale parameter is a = ( 1 + z ) ^ { -1 } \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } 1 , the slope is \gamma \approx 3 as in the NFW profile , but \gamma \approx 4 at a > 1 when \Omega _ { \Lambda } \sim 1 and the universe is inflating .
The shape of the DM profiles presents a significant scatter around the mean .
It is therefore important to analyse a significant statistical sample of halos in order to determine the mean profile .

I compare the DM profiles in the 1 h ^ { -1 } Mpc box with the same simulation including stars , baryons and radiative transfer presented by Ricotti , Gnedin and Shull .
Radiative feedback effects produce a larger scatter in the density profile shapes but , on average , do not affect the shape of the DM profiles significantly .