Influence of Plasma Collective Effects on Cosmological Evolution

TL;DR

This paper explores how plasma collective effects, often ignored, can influence large-scale structure formation and CMB anisotropy, revealing a potential suppression of matter power spectrum at certain scales.

Contribution

It provides a more comprehensive derivation of the Maxwell-Einstein-Boltzmann equation and assesses plasma effects on both structure formation and CMB anisotropy.

Findings

Plasma effects may suppress matter power spectrum at scales k>1h Mpc^{-1}.

The impact on CMB anisotropy is negligible.

Theoretical formulation is extended for better accuracy.

Abstract

It is well-known that the universe was in a plasma state both before decoupling and after reionization. However, the conventional wisdom has been that the plasma effects are largely Debye-shielded and can thus be safely ignored when considering large scale evolutions. Recently we showed that large scale structure formation in the universe may actually be suppressed by the plasma collective effect. Indeed, observational data indicate that the conventional theoretical formula tends to overestimate the matter power spectrum at scales $k>1h{\rm Mpc}^{-1}$. In this paper, we further develop our theory through a more thorough and general derivation of the Maxwell-Einstein-Boltzmann equation. In addition to baryon density perturbation post reionization, we apply this general formulation to investigate the possible plasma effect on CMB anisotropy. As expected, while the plasma effect does render an observable effect to the former, its impact on the latter is totally negligible.