Modified Gravity N-body Code Comparison Project

TL;DR

This paper compares different N-body simulation codes for modified gravity models, demonstrating they agree within 1% for key observables, thus supporting their use in upcoming large-scale structure surveys.

Contribution

It provides the first detailed comparison of N-body codes for f(R), DGP, and Symmetron models, confirming their accuracy and agreement for cosmological observables.

Findings

Codes agree within 1% for matter power spectrum up to k~10 h/Mpc

Good agreement in halo properties and velocity divergence spectra

Quasi-static approximation is valid for all models tested

Abstract

Self-consistent ${\it N}$-body simulations of modified gravity models are a key ingredient to obtain rigorous constraints on deviations from General Relativity using large-scale structure observations. This paper provides the first detailed comparison of the results of different ${\it N}$-body codes for the $f(R)$, DGP, and Symmetron models, starting from the same initial conditions. We find that the fractional deviation of the matter power spectrum from $\Lambda$CDM agrees to better than $1\%$ up to $k \sim 5-10~h/{\rm Mpc}$ between the different codes. These codes are thus able to meet the stringent accuracy requirements of upcoming observational surveys. All codes are also in good agreement in their results for the velocity divergence power spectrum, halo abundances and halo profiles. We also test the quasi-static limit, which is employed in most modified gravity ${\it N}$-body codes, for the Symmetron model for which the most significant non-static effects among the models considered are expected. We conclude that this limit is a very good approximation for all of the observables considered here.