Nonlinear Power Spectrum from Resummed Perturbation Theory: a Leap Beyond the BAO Scale

TL;DR

This paper introduces a fast, accurate computational scheme for the nonlinear matter power spectrum in cosmology, achieving percent-level agreement with simulations and suitable for weak lensing studies.

Contribution

The authors develop a novel time-evolution based method for computing the nonlinear power spectrum that is computationally efficient and accurate across relevant scales.

Findings

Achieves percent-level accuracy with N-body simulations in the BAO range.

Provides a fast computation comparable to 1-loop calculations.

Applicable to weak lensing scales up to k ~ 1 h/Mpc at z >= 0.5.

Abstract

A new computational scheme for the nonlinear cosmological matter power spectrum (PS) is presented. Our method is based on evolution equations in time, which can be cast in a form extremely convenient for fast numerical evaluations. A nonlinear PS is obtained in a time comparable to that needed for a simple 1-loop computation, and the numerical implementation is very simple. Our results agree with N-body simulations at the percent level in the BAO range of scales, and at the few-percent level up to $k ~ 1$ h/Mpc at $z >= 0.5$, thereby opening the possibility of applying this tool to scales interesting for weak lensing. We clarify the approximations inherent to this approach as well as its relations to previous ones, such as the Time Renormalization Group, and the multi-point propagator expansion. We discuss possible lines of improvements of the method and its intrinsic limitations by multi streaming at small scales and low redshifts.