Mass density vs. energy density at cosmological scales

TL;DR

This paper derives and tests a formula relating matter energy density and mass density power spectra in the b1CDM model, revealing significant divergence at large cosmological scales through N-body simulations.

Contribution

It introduces a new formula linking energy and mass density power spectra and validates it with large-scale N-body simulations.

Findings

The formula accurately relates energy and mass density spectra.

Power spectra diverge significantly at large scales.

Validation confirms the theoretical relation within b1CDM.

Abstract

In the presence of the gravitational field, the energy density of matter no longer coincides with its mass density. A discrepancy exists, of course, also between the associated power spectra. Within the $\Lambda$CDM model, we derive a formula that relates the power spectrum of the energy density to that of the mass density and test it with the help of N-body simulations run in comoving boxes of 2.816 Gpc/$h$. The results confirm the validity of the derived formula and simultaneously show that the power spectra diverge significantly from one another at large cosmological scales.