The radiation energy component of the Hubble function and a LCDM cosmological simulation

TL;DR

This paper investigates how including the radiation energy component Omega_r in a LCDM cosmological simulation affects large-scale structure formation, revealing significant impacts on power spectrum, halo mass function, and halo concentration.

Contribution

It provides the first detailed analysis of Omega_r's effects on structure formation in a high-redshift LCDM simulation, highlighting its importance in nonlinear evolution.

Findings

50% reduction in matter power spectrum across scales

20% decrease in halo concentration with Omega_r included

Omega_r significantly influences large-scale structure evolution

Abstract

We study some effects the inclusion of the radiation energy component in the universe, Omega_r, can have on several quantities of interest for the large-scale structure of the universe in a LCDM cosmological simulation; started at a very high redshift (z=500). In particular we compute the power spectrum density, the halo mass function, and the concentration-mass relation for haloes. We find that Omega_r has an important contribution in the long-term nonlinear evolution of structures in the universe. For instance, a lower matter density power, by approx 50%, in all scales is obtained when compared with a simulation without the radiation term. Also, haloes formed with the Omega_r taken into account are approx 20% less concentrated than when not included in the Hubble function.