  Based on a suite of N-body simulations of the Hu-Sawicki model of f(R)
gravity with different sets of model and cosmological parameters, we develop a
new fitting formula with a numeric code, MGHalofit, to calculate the nonlinear
matter power spectrum P(k) for the Hu-Sawicki model. We compare the MGHalofit
predictions at various redshifts (z<=1) to the f(R) simulations and find that
the accuracy on P(k) is 6% at k<1 h/Mpc and 12% at 1<k<10 h/Mpc respectively.
Based on a sensitivity study of an ongoing and a future spectroscopic survey,
we estimate the detectability of a signal of modified gravity described by the
Hu-Sawicki model using the power spectrum up to quasi-nonlinear scales.
MGHalofit is publicly available at
http://icosmology.info/website/MGHalofit.html.
