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FORGE - the f(R) gravity cosmic emulator project I: Introduction and matter power spectrum emulator

Arnold, Christian; Li, Baojiu; Giblin, Benjamin; Harnois-Déraps, Joachim; Cai, Yan-Chuan

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Christian Arnold

Benjamin Giblin

Joachim Harnois-Déraps

Yan-Chuan Cai


We present a large suite of cosmological simulations, the FORGE (F-of-R Gravity Emulator) simulation suite, which is designed to build accurate emulators for cosmological observables in galaxy clustering, weak gravitational lensing, and galaxy clusters for the f(R)-gravity model. A total of 200 simulations explore the cosmological parameter space around a standard Planck cosmology with a Latin hypercube, for 50 combinations of f¯R0⁠, Ωm, σ8, and h with all other parameters fixed. For each parameter combination, or node, we ran four independent simulations, one pair using 10243 particles in 500h−1Mpc simulation boxes to cover small scales, and another pair using 5123 simulation particles in 1.5h−1Gpc boxes for larger scales. Each pair of initial conditions is selected such that sample variance on large scales is minimized on average. In this work we present an accurate emulator for the matter power spectrum in f(R) gravity trained on FORGE. We have verified, using the cross-validation technique, that the emulator accuracy is better than 2.5percent for the majority of nodes, particularly around the centre of the explored parameter space, up to scales of k=10hMpc−1⁠. We have also checked the power spectrum emulator against simulations that are not part of our training set and found excellent agreement. Due to its high accuracy on small scales, the FORGE matter power spectrum emulator is well suited for weak-lensing analysis and can play a key tool in constraining f(R) gravity using current and future observational data.


Arnold, C., Li, B., Giblin, B., Harnois-Déraps, J., & Cai, Y. (2022). FORGE - the f(R) gravity cosmic emulator project I: Introduction and matter power spectrum emulator. Monthly Notices of the Royal Astronomical Society, 515(3), 4161-4175.

Journal Article Type Article
Acceptance Date Mar 28, 2022
Online Publication Date Aug 10, 2022
Publication Date 2022-09
Deposit Date Oct 27, 2021
Publicly Available Date Aug 24, 2022
Journal Monthly Notices of Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 515
Issue 3
Pages 4161-4175
Public URL
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Published Journal Article (2.7 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2022 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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