FREmu: Power Spectrum Emulator for f(R) Gravity

Abstract

To investigate gravity in the nonlinear regime of cosmic structure using measurements from stage IV surveys, it is imperative to accurately compute large-scale structure observables, such as nonlinear matter power spectra, for gravity models that extend beyond general relativity. However, the theoretical predictions of nonlinear observables are typically derived from N -body simulations, which demand substantial computational resources. In this study, we introduce a novel public emulator, termed FREmu , designed to provide rapid and precise forecasts of nonlinear power spectra specifically for the Hu–Sawicki f ( R ) gravity model across scales 0.0089 h Mpc ^−1 < k < 0.5 h Mpc ^−1 and redshifts 0 < z < 3. FREmu leverages principal component analysis and artificial neural networks to establish a mapping from parameters to power spectra, utilizing training data derived from the Quijote-MG simulation suite. With a parameter space encompassing seven dimensions, including Ω _m , Ω _b , h , n _s , σ _8 , M _ν , and ${f}_{{R}_{0}}$ , the emulator achieves an accuracy exceeding 95% for the majority of cases, thus proving to be highly efficient for constraining parameters.

Keywords

• Cosmology
• Large-scale structure of the universe
• Non-standard theories of gravity