Moving around the cosmological parameter space: a nonlinear power spectrum reconstruction based on high-resolution cosmic responses

TL;DR

This paper introduces a method to accurately interpolate the nonlinear cosmic power spectrum across different cosmological parameters using response functions and a new Python package, RESPRESSO, based on extensive simulations.

Contribution

It develops a numerical response function measurement and an analytical model to interpolate the nonlinear power spectrum over cosmological parameters, enhancing accuracy and efficiency.

Findings

Response function measurement from 1,400 simulations

The analytical model improves spectrum interpolation accuracy

RESPRESSO package enables practical application of the method

Abstract

We present numerical measurements of the power spectrum response function of the gravitational growth of cosmic structures, defined as the functional derivative of the nonlinear spectrum with respect to the linear counterpart, based on $1,400$ cosmological simulations. We develop a simple analytical model based on a regularization of the standard perturbative calculation. Using the model prediction, we show that this function gives a natural way to interpolate the nonlinear power spectrum over cosmological parameter space from single or multi-step interpolations. We demonstrate that once an accurate numerical spectrum template is available for one (or a small number of) cosmological model(s), it doubles the range in $k$ for which percent level accuracy can be obtained even for large change in the cosmological parameters. The python package RESPRESSO we developed to make those predictions is publicly available.