Testing f(R) Gravity from Cosmic Shear Measurements

In this work, we perform a detailed analysis to constrain the Hu–Sawicki f ( R ) gravity model, using cosmic shear data from three prominent Stage-III weak lensing surveys: Dark Energy Survey Year 3, KiDS-1000, and Hyper Suprime-Cam Year 3. To accurately model the nonlinear matter clustering in the analysis of cosmic shear signals, we employ FREmu , a recently developed power spectrum emulator for the f ( R ) gravity trained on the Quijote-MG simulations. This emulator achieves precise predictions, limiting the errors to 5% on scales of 0.009 h Mpc −1 < k < 0.5 h Mpc −1 . Our findings reveal that cosmic shear data alone impose only weak constraints on the f ( R ) parameter log 10 ∣ f R 0 ∣ . To improve these constraints, we incorporate state-of-the-art external observations, including data from the cosmic microwave background and baryon acoustic oscillations. The inclusion of these external data sets significantly enhances the constraints, yielding an upper limit of log 10 ∣ f R 0 ∣ < − 4.98 at the 95% confidence level.