Discreteness effects in simulations of hot/warm dark matter

By Jie-Shuang Wang, Simon D. M. White. 2007

194 citations recorded by the source corpus.

In hot/warm dark matter (HDM/WDM) universes the density fluctuations at early times contain very little power below a characteristic wavelength related inversely to the particle mass. We study how discreteness noise influences the growth of non-linear structures smaller than this coherence scale in N-body simulations of cosmic structure formation. It has been known for 20 yr that HDM simulations in which the initial uniform particle load is a cubic lattice exhibit artefacts related to this lattice. In particular, the filaments which form in such simulations break up into regularly spaced clumps which reflect the initial grid pattern. We demonstrate that a similar artefact is present even when the initial uniform particle load is not a lattice, but rather a glass with no preferred directions and no long-range coherence. Such regular fragmentation also occurs in simulations of the collapse of idealized, uniform filaments, although not in simulations of the collapse of infinite uniform sheets. In HDM or WDM simulations all self-bound non-linear structures with masses much smaller than the free streaming mass appear to originate through spurious fragmentation of filaments. These artificial fragments form below a characteristic mass which scales as *m1/3p k-2peak,, where mp is the N-body particle mass and k peak is the wavenumber at the maximum of k 3 P(k)[P(k) is the power spectrum]. This has the unfortunate consequence that the effective mass resolution of such simulations improves only as the cube root of the number of particles employed.

Subfields: Astronomy and Astrophysics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/e8bf9ca18dff739171970268af9e9f2d87a411bd

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Citations in the corpus

Massive neutrinos and the non‐linear matter power spectrum (2011, background): “One potential problem with particle based simulations is thermal shot noise from the finite sampling of the neutrino distribution (Wang & White 2007), especially for the higher thermal velocities encountered at high redshift or for particularly low mass neutrinos.”
The effect of neutrinos on the matter distribution as probed by the intergalactic medium (2010, background): “The last effect that we examine here is the dependence of the matter power spectrum on the initial redshift of the simulation [44, 45].”
The properties of warm dark matter haloes (2013, methodology): “N-body simulations with a resolved cutoff in the initial power spectrum undergo artificial fragmentation in filaments (Bode et al. 2001; Wang & White 2007).”
Subhaloes in self-interacting galactic dark matter haloes (2012, unknown): “High resolution simulations within the WDM cosmogony are however challenging (Wang & White 2007) and hence a consensus on the inner density profile of WDM haloes has not been reached.”
Halo mass function and the free streaming scale (2013, background): “In the simulation outputs these artefacts are most visible in cosmic filaments, where they form equally spaced clumps that are strongly resolution dependent (Wang & White 2007; Schneider et al. 2012).”
CONTRASTING GALAXY FORMATION FROM QUANTUM WAVE DARK MATTER, ψDM, WITH ΛCDM, USING PLANCK AND HUBBLE DATA (2015, background): “These spurious halos are caused by artificial fragmentation due to numerical artifacts (Wang & White 2007), and are mostly confined along cosmic filaments (see Figure 3, upper panel).”
ETHOS - an effective theory of structure formation: dark matter physics as a possible explanation of the small-scale CDM problems (2015, background): “As we know, self-interactions will affect the internal structure of haloes at late 2 We note that according to the study by Wang & White 2007, the limiting mass below which discreteness effects are important is given by Mlim = 10.1Ωmρcritdk −2 peak, where d is the interparticle separation, and…”
The warm dark matter halo mass function below the cut-off scale (2013, background): “This phenomenon originates in the numerical (unphysical) fragmentation of filaments, and it exceeds by far the population of real WDM haloes on scales near the cut-off scale (see e.g. Avila-Reese et al. 2001; Bode et al. 2001; Wang & White 2007; Melott 2007).”
A fundamental problem in our understanding of low-mass galaxy evolution (2012, background): “At this halo mass, no compelling evidence of spurious structure (see e.g. Wang & White 2007) was found in the simulation”
THE VELOCITY FUNCTION IN THE LOCAL ENVIRONMENT FROM ΛCDM AND ΛWDM CONSTRAINED SIMULATIONS (2009, methodology): “At the low mass end we see discreteness features as described in Wang & White (2007).”
The haloes of bright satellite galaxies in a warm dark matter universe (2011, background): “…we find similar results but the conclusions of these early simulations are difficult to interpret because, as we shall see later, the sharp cutoff in the power spectrum gives rise to the formation of a large number of artificial haloes that are purely numerical in origin (Wang & White 2007).”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, unknown): “One can then either i) run simulations [194, 219, 1268, 1222, 335, 1209, 1056, 161, 68, 1073], ii) use the halo model [1107, 1056, 437] or iii) a fit analogous to Equation 2.”
Dark matter halo merger histories beyond cold dark matter – I. Methods and application to warm dark matter (2012, background): “The issue of spurious haloes formed by the fragmentation of filaments due to numerical noise (Wang & White 2007) is investigated in Lovell et al. (in preparation).”
Non-linear evolution of cosmological structures in warm dark matter models (2011, background): “This enables us to differentiate between genuine structures and spurious structures, which can collapse out of the initial particle lattice (cf. Wang & White 2007; Polisensky & Ricotti 2011).”
The stellar mass-halo mass relation of isolated field dwarfs : a critical test of ΛCDM at the edge of galaxy formation (2016, background): “5 There is a known problem in the literature with the formation of spurious halos at the resolution limit in WDM simulations (e.g. Wang & White 2007; Hahn et al. 2013; Angulo et al. 2013; Lovell et al. 2014; Hobbs et al. 2015).”
Cores in warm dark matter haloes: a Catch 22 problem (2012, methodology): “Numerical N-body simulations have been used to better understand the properties of virialized objects in the Warm Dark Matter scenarios (e.g. Bode et al. 2001; Knebe et al. 2003; Wang & White 2007; Zavala et al. 2009; Tikhonov et al. 2009; Schneider et al. 2011).”