The order parameters Q l are shown in Figs. 1 the time evolution of Q l is plotted as a function of l for different epochs. The scatter in the numerical ensemble can be judged from the size of the error bars, for the sake of clarity they have been shown in each plot only for a single case. For the plot of Fig. 1 the point distribution is that obtained from the set. In this case the computation of the Q l can be greatly reduced by using a random sub-sample of the particle set.
Error bars show the scatter within the five simulation ensemble.
How the Q l change when particle populations with different clustering properties are selected is shown in Fig. 2 . For any l the coefficients Q l get larger when higher thresholds are selected. The choice of higher corresponds to a more clustered distribution, and this is clearly detected by the coefficients Q l . The angular power spectrum coefficients C l scale approximately as , thus the enhanced clustering of particle subsets associated with higher is masked for the C l by the drop in N i , with respect lower thresholds. In this case the comparison has been made for the population , in order to avoid errors introduced by a linear bias approximation for Eq.