  By means of N-body simulations, we study early structure formation in the
presence of a scaling distribution of cosmic string loops. Cosmic string loops
dominate the high redshift halo mass function while the fluctuations seeded by
the standard structure formation scenario dominate structure at low redshifts.
In our study, the effects of the cosmic string loops are taken into account by
displacing the dark matter particles and their velocities at the initial time
of the simulation by amounts determined by the analytical analysis which makes
use of the Zeldovich approximation. We find that the resulting halo mass
function is to a good approximation given by the sum of the analytically
determined cosmic string halo mass function and the halo mass function obtained
from the standard $\Lambda$CDM model.
