Precision modelling of the matter power spectrum in a Planck-like Universe

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 non-linear matter power spectrum. We restrict attention to parameters in the vicinity of the Planck Collaboration's best fit. On large scales (k less than or similar to 0.07 h Mpc(-1)), our model evaluates the two-loop calculation from the multipoint propagator theory of Bernardeau et al. On smaller scales (k greater than or similar to 0.7 h Mpc(-1)), we transition to a smoothing-spline-fit model, that characterizes the differences between the Takahashi et al. 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 cold dark matter 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 less than or similar to 1 per cent 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 less than or similar to 3 per cent over the hypercube: w(0) is an element of {-1.05, -0.95}, w(a) is an element of {-0.4, 0.4}, Omega(m, 0) is an element of {0.21, 0.4}, omega(c) is an element of {0.1, 0.13}, omega(b) is an element of {2.0, 2.4}, n(s) is an element of{0.85, 1.05}, A(s) is an element of{1.72 x 10(-9), 2.58 x 10(-9)}, alpha is an element of {-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://Cosmolog yCode@bitbucket.org/ngenhalofitteam/ngenhalofitpublic.git.