  We perform N-body simulations of theories with infinite-volume extra
dimensions, such as the Dvali-Gabadadze-Porrati (DGP) model and its
higher-dimensional generalizations, where 4D gravity is mediated by massive
gravitons. The longitudinal mode of these gravitons mediates an extra scalar
force, which we model as a density-dependent modification to the Poisson
equation. This enhances gravitational clustering, particularly on scales that
have undergone mild nonlinear processing. While the standard non-linear fitting
algorithm of Smith et al. overestimates this power enhancement on non-linear
scales, we present a modified fitting formula that offers a remarkably good fit
to our power spectra. Due to the uncertainty in galaxy bias, our results are
consistent with precision power spectrum determinations from galaxy redshift
surveys, even for graviton Compton wavelengths as small as 300 Mpc. Our model
is sufficiently general that we expect it to capture the phenomenology of a
wide class of related higher-dimensional gravity scenarios.
