Relativistic secondorder initial conditions for simulations of largescale structure
Abstract
Relativistic corrections to the evolution of structure can be used to test general relativity on cosmological scales. They are also a wellknown systematic contamination in the search for a primordial nonGaussian signal. We present a numerical framework to generate RELativistic secondorder Initial Conditions ($\texttt{RELIC}$) based on a generic (not necessarily separable) secondorder kernel for the density perturbations. In order to keep the time complexity manageable we introduce a scale cut that separates long and short scales, and neglect the "shortshort" coupling that will eventually be swamped by uncontrollable higherorder effects. To test our approach, we use the secondorder EinsteinBoltzmann code $\texttt{SONG}$ to provide the numerical secondorder kernel in a $\Lambda$CDM model, and we demonstrate that the realisations generated by $\texttt{RELIC}$ reproduce the bispectra well whenever at least one of the scales is a "long" mode. We then present a generic algorithm that takes a perturbed density field as an inputand provides particle initial data that matches this input to arbitrary order in perturbations for a given particlemesh scheme. We implement this algorithm in the relativistic Nbody code $\texttt{gevolution}$ to demonstrate how our framework can be used to set precise initial conditions for cosmological simulations of largescale structure.
 Publication:

arXiv eprints
 Pub Date:
 October 2021
 arXiv:
 arXiv:2110.11249
 Bibcode:
 2021arXiv211011249A
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 24 pages, 7 figures