Discreteness Effects in Lambda Cold Dark Matter Simulations: A Wavelet-Statistical View

TL;DR

This study investigates how particle discreteness impacts LambdaCDM N-body simulations, using wavelet-based statistical analysis to understand the effects and provide guidelines for simulation resolution.

Contribution

It introduces a wavelet-statistical approach to analyze discreteness effects and clarifies the resolution condition epsilon ~ 2d for accurate cosmological simulations.

Findings

Discreteness noise does not propagate from small to large scales during evolution.

The optimal force resolution should be approximately twice the interparticle distance.

Wavelet statistics effectively diagnose discreteness effects in simulations.

Abstract

The effects of particle discreteness in N-body simulations of Lambda Cold Dark Matter (LambdaCDM) are still an intensively debated issue. In this paper we explore such effects, taking into account the scatter caused by the randomness of the initial conditions, and focusing on the statistical properties of the cosmological density field. For this purpose, we run large sets of LambdaCDM simulations and analyse them using a large variety of diagnostics, including new and powerful wavelet statistics. Among other facts, we point out (1) that dynamical evolution does not propagate discreteness noise up from the small scales at which it is introduced, and (2) that one should aim to satisfy the condition epsilon ~ 2d, where "epsilon" is the force resolution and "d" is the interparticle distance. We clarify what such a condition means, and how to implement it in modern cosmological codes.