The measurement of the absolute neutrino mass scale from cosmological
large-scale clustering data is one of the key science goals of the Euclid
mission. Such a measurement relies on precise modelling of the impact of
neutrinos on structure formation, which can be studied with $N$ -body
simulations. Here we present the results from a major code comparison effort to
establish the maturity and reliability of numerical methods for treating
massive neutrinos. The comparison includes eleven full $N$ -body implementations
(not all of them independent), two $N$ -body schemes with approximate time
integration, and four additional codes that directly predict or emulate the
matter power spectrum. Using a common set of initial data we quantify the
relative agreement on the nonlinear power spectrum of cold dark matter and
baryons and, for the $N$ -body codes, also the relative agreement on the
bispectrum, halo mass function, and halo bias. We find that the different
numerical implementations produce fully consistent results. We can therefore be
confident that we can model the impact of massive neutrinos at the sub-percent
level in the most common summary statistics. We also provide a code validation
pipeline for future reference.

PREPRINT

# Euclid: Modelling massive neutrinos in cosmology -- a code comparison

J. Adamek, R. E. Angulo, C. Arnold, M. Baldi, M. Biagetti, B. Bose, C. Carbone, T. Castro, J. Dakin, K. Dolag, W. Elbers, C. Fidler, C. Giocoli, S. Hannestad, F. Hassani, C. Hernández-Aguayo, K. Koyama, B. Li, R. Mauland, P. Monaco, C. Moretti, D. F. Mota, C. Partmann, G. Parimbelli, D. Potter, A. Schneider, S. Schulz, R. E. Smith, V. Springel, J. Stadel, T. Tram, M. Viel, F. Villaescusa-Navarro, H. A. Winther, B. S. Wright, M. Zennaro, N. Aghanim, L. Amendola, N. Auricchio, D. Bonino, E. Branchini, M. Brescia, S. Camera, V. Capobianco, V. F. Cardone, J. Carretero, F. J. Castander, M. Castellano, S. Cavuoti et al.

Submitted on 22 November 2022

## Abstract

## Preprint

Comment: 43 pages, 17 figures, 2 tables; published on behalf of the Euclid Consortium; data available at https://doi.org/10.5281/zenodo.7297976

Subject: Astrophysics - Cosmology and Nongalactic Astrophysics