We use a suite of high-resolution N -body simulations and state-of-the-art perturbation theory to improve the code halofit , which predicts the nonlinear matter power spectrum .
We restrict attention to parameters in the vicinity of the Planck Collaboration ’ s best fit .
On large-scales ( k \lesssim 0.07 h { Mpc } ^ { -1 } ) , our model evaluates the 2-loop calculation from the Multi-point Propagator Theory of Bernardeau et al .
( 2012 ) .
On smaller scales ( k \gtrsim 0.7 h { Mpc } ^ { -1 } ) , we transition to a smoothing-spline-fit model , that characterises the differences between the Takahashi et al .
( 2012 ) recalibration of halofit2012 and our simulations .
We use an additional suite of simulations to explore the response of the power spectrum to variations in the cosmological parameters .
In particular , we examine : the time evolution of the dark energy equation of state ( w _ { 0 } , w _ { a } ) ; the matter density \Omega _ { m } ; the physical densities of CDM and baryons ( \omega _ { c } , \omega _ { b } ) ; and the primordial power spectrum amplitude A _ { s } , spectral index n _ { s } , and its running \alpha .
We construct correction functions , which improve halofit ’ s dependence on cosmological parameters .
Our newly calibrated model reproduces all of our data with \lesssim 1 \% precision .
Including various systematic errors , such as choice of N -body code , resolution , and through inspection of the scaled second order derivatives , we estimate the accuracy to be \lesssim 3 \% over the hyper-cube : w _ { 0 } \in \ { -1.05 , -0.95 \ } , w _ { a } \in \ { -0.4 , 0.4 \ } , \Omega _ { m, 0 } \in \ { 0.21 , 0.4 \ } , \omega _ { c } \in \ { 0.1 , 0.13 \ } , \omega _ { b } \in \ { 2.0 , 2.4 \ } , n _ { s } \in \ { 0.85 , 1.05 \ } , A _ { s } \in \ { 1.72 \times 10 ^ { -9 } , 2.58 \times 10 ^ { -9 } \ } , \alpha \in \ { -0.2 , 0.2 \ } up to k = 9.0 h { Mpc } ^ { -1 } and out to z = 3 .
Outside of this range the model reverts to halofit2012 .
We release all power spectra data with the C-code NGenHalofit at : https : //CosmologyCode @ bitbucket.org/ngenhalofitteam/ngenhalofitpublic.git .