Increasing Fisher Information by Moving-Mesh Reconstruction

TL;DR

This paper introduces a Moving-Mesh reconstruction technique in cosmology that significantly enhances Fisher information in matter power spectra, improving the extraction of linear modes from nonlinear data.

Contribution

The paper presents a novel Moving-Mesh algorithm for reconstruction that markedly increases Fisher information, aiding in linear mode recovery from nonlinear matter distributions.

Findings

Fisher information increased by a factor of ~50 after reconstruction.

Nonlinear plateau of Fisher information is significantly extended.

Technique benefits studies of BAO, RSD, and cosmic neutrinos.

Abstract

Reconstruction techniques are commonly used in cosmology to reduce complicated nonlinear behaviours to a more tractable linearized system. We study a new reconstruction technique that uses the Moving-Mesh algorithm to estimate the displacement field from nonlinear matter distribution. We show the performance of this new technique by quantifying its ability to reconstruct linear modes. We study the cumulative Fisher information $I(<k_n)$ about the initial matter power spectrum in the matter power spectra in 130 $N$-body simulations before and after reconstruction, and find that the nonlinear plateau of $I(<k_n)$ is increased by a factor of $\sim 50$ after reconstruction, from $I \simeq 2.5 \times 10^{-5} /({\rm Mpc}/h)^3$ to $I \simeq 1.3 \times 10^{-3}/({\rm Mpc}/h)^3$ at large $k$. This result includes the decorrelation between initial and final fields, which has been neglected in some previous studies. We expect this technique to be beneficial to problems such as baryonic acoustic oscillations, redshift space distortions and cosmic neutrinos that rely on accurately disentangling nonlinear evolution from underlying linear effects.