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Matter power spectrum and the challenge of percent accuracy

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posted on 2023-06-09, 02:24 authored by Aurel Schneider, Romain Teyssier, Doug Potter, Joachim Stadel, Julian Onions, Darren S Reed, Robert E SmithRobert E Smith, Volker Springel, Frazer R Pearce, Roman Scoccimarro
Future galaxy surveys require one percent precision in the theoretical knowledge of the power spectrum over a large range including very nonlinear scales. While this level of accuracy is easily obtained in the linear regime with perturbation theory, it represents a serious challenge for small scales where numerical simulations are required. In this paper we quantify the precision of present-day N -body methods, identifying main potential error sources from the set-up of initial conditions to the measurement of the final power spectrum. We directly compare three widely used N -body codes, Ramses, Pkdgrav3, and Gadget3 which represent three main discretisation techniques: the particle-mesh method, the tree method, and a hybrid combination of the two. For standard run parameters, the codes agree to within one percent at k=1 hMpc -1 and to within three percent at k=10 hMpc -1. We also consider the bispectrum and show that the reduced bispectra agree at the sub-percent level for k=2 hMpc -1 . In a second step, we quantify potential errors due to initial conditions, box size, and resolution using an extended suite of simulations performed with our fastest code Pkdgrav3. We demonstrate that the simulation box size should not be smaller than L=0.5 h -1 Gpc to avoid systematic finite-volume effects (while much larger boxes are required to beat down the statistical sample variance). Furthermore, a maximum particle mass of M p =10 9 h -1 M ? is required to conservatively obtain one percent precision of the matter power spectrum. As a consequence, numerical simulations covering large survey volumes of upcoming missions such as DES, LSST, and Euclid will need more than a trillion particles to reproduce clustering properties at the targeted accuracy.

Funding

TB002-46; Dept P&A

History

Publication status

  • Published

File Version

  • Accepted version

Journal

Journal of Cosmology and Astroparticle Physics

ISSN

1475-7516

Publisher

IOP Publishing

Issue

04

Volume

2016

Page range

047-047

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2016-08-05

First Open Access (FOA) Date

2017-04-27

First Compliant Deposit (FCD) Date

2016-08-05

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