Accurate initial conditions for cosmological N-body simulations: Minimizing truncation and discreteness errors

Understand

Inaccuracies in the initial conditions for cosmological N-body simulations could easily be the largest source of systematic error in predicting the non-linear large-scale structure.

• From the theory side, initial conditions are usually provided by using low-order truncations of the displacement field from Lagrangian perturbation theory, with the first and second-order approximations being the most common ones.
• Here we investigate the improvement brought by using initial conditions based on third-order Lagrangian perturbation theory (3LPT).
• We show that with 3LPT, truncation errors are vastly suppressed, thereby opening the portal to initializing simulations accurately as late as z=12 (for the resolution we consider).