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Abstract

I study the effects of Hu & Sawicki f(R)-gravity on astrophysical processes and cosmological observables. Employing hydrodynamical cosmological simulations carried out with the MG-GADGET and AREPO codes in modified gravity the influences on the Lyman-alpha forest, Milky-Way sized halos, clustering and lensing on large scales as well as on the Sunyaev-Zeldovich effect are investigated. Comparing MG-GADGET to other codes I find that different f(R)-gravity simulation methods agree on a percent-level accuracy for matter power spectra and halo profiles. The f(R) effects are in general smaller at higher redshift, resulting in very small differences between f(R)-gravity and general relativity (GR) for the Lyman-alpha forest. Structural properties of Milky-Way sized halos are however altered by up to 40%. Requiring that the Solar system is screened within the Milky-Way leads to f_R0 = -10^-7 as a constraint on the background parameter. The fifth force is well described by a theoretical approximation in ideal NFW-halos while this estimate is much less accurate for realistic halos. Two point correlation functions and angular power spectra are increased in f(R)-gravity compared to GR. Dark matter halos are in contrast less strongly correlated, leading to a lower halo clustering bias in f(R)-gravity. The angular power in both thermal and kinetic Sunyaev-Zeldovich maps is by a few percent higher in modified gravity compared to a LCDM model.