Date Published:

October 1, 2016

Abstract:

In cosmological N-body simulations, the representation of dark matter asdiscrete `macroparticles' suppresses the growth of structure, such thatsimulations no longer reproduce linear theory on small scales neark_Nyquist. Marcos et al. demonstrate that this is due tosparse sampling of modes near k_Nyquist and that theoften-assumed continuum growing modes are not proper growing modes ofthe particle system. We develop initial conditions (ICs) that respectthe particle linear theory growing modes and then rescale the modeamplitudes to account for growth suppression. These ICs also allow us totake advantage of our very accurate N-body code ABACUS to implementsecond-order Lagrangian perturbation theory (2LPT) in configurationspace. The combination of 2LPT and rescaling improves the accuracy ofthe late-time power spectra, halo mass functions, and halo clustering.In particular, we achieve 1 per cent accuracy in the power spectrum downto k_Nyquist, versus k_Nyquist/4 without rescalingor k_Nyquist/13 without 2LPT, relative to an oversampledreference simulation. We anticipate that our 2LPT will be useful forlarge simulations where fast Fourier transforms are expensive and thatrescaling will be useful for suites of medium-resolution simulationsused in cosmic emulators and galaxy survey mock catalogues. Code togenerate ICs is available at https://github.com/lgarrison/zeldovich-PLT.

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