Transients from initial conditions based on Lagrangian perturbation theory in N-body simulations

概要

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We explore the initial conditions for cosmological N-body simulationssuitable for calculating the skewness and kurtosis of the density field. In general, theinitial conditions based on the perturbation theory (PT) provide incorrect second-orderand higher-order growth. These errors implied by the use of the perturbation theory toset up the initial conditions in N-body simulations are called transients. Unless thesetransients are completely suppressed compared with the dominant growing mode, wecan not reproduce the correct evolution of cumulants with orders higher than two, eventhough there is no problem with the numerical scheme. We investigate the impact oftransients on the observable statistical quantities by performing N-body simulationswith initial conditions based on Lagrangian perturbation theory (LPT). We show thatthe effects of transients on the kurtosis from the initial conditions, based on secondorderLagrangian perturbation theory (2LPT) have almost disappeared by z ∼ 5, aslong as the initial conditions are set at z > 30. This means that for practical purposes,the initial conditions based on 2LPT are accurate enough for numerical calculations ofskewness and kurtosis.
2007-12-00