Clipping the cosmos. II. Cosmological information from nonlinear scales

We present a method for suppressing contributions from higher-order terms in perturbation theory, greatly increasing the amount of information that may be extracted from the matter power spectrum. In an evolved cosmological density field the highest density regions are responsible for the bulk of the nonlinear power. By suitably down-weighting these problematic regions we find that the one- and two-loop terms are typically reduced in amplitude by $\ensuremath{\sim}70%$ and $\ensuremath{\sim}95%$, respectively, relative to the linear power spectrum. This greatly facilitates modeling the shape of the galaxy power spectrum, potentially increasing the number of useful Fourier modes by more than 2 orders of magnitude. We provide a demonstration of how this technique allows the galaxy bias and the amplitude of linear matter perturbations ${\ensuremath{\sigma}}_{8}$ to be determined from the power spectrum on conventionally nonlinear scales, $0.1<k<0.7\text{ }h{\mathrm{Mpc}}^{\ensuremath{-}1}$.