Grid-based initial conditions imprint roughly one-percent alignment artifacts on simulated halo shapes, with a redshift-dependent sign flip whose origin is not yet pinned down.
An alternative to grids and glasses: Quaquaversal pre-initial conditions for N-body simulations
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abstract
N-body simulations sample their initial conditions on an initial particle distribution, which for cosmological simulations is usually a glass or grid, whilst a Poisson distribution is used for galaxy models, spherical collapse etc. These pre-initial conditions have inherent correlations, noise due to discreteness and preferential alignments, whilst the glass distribution is poorly defined and computationally expensive to construct. We present a novel particle distribution which can be useful as a pre-initial condition for N-body simulations, using a simple construction based on a ``quaquaversal'' tiling of space. This distribution has little preferred orientation (i.e. is statistically isotropic), has a rapidly vanishing large scale power-spectrum (P(k) ~ k^4), and is trivial to create. It should be particularly useful for warm dark matter and cold collapse simulations.
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Artifacts in Halo Shapes: Imprints of the Initial Condition
Grid-based initial conditions imprint roughly one-percent alignment artifacts on simulated halo shapes, with a redshift-dependent sign flip whose origin is not yet pinned down.