Electromagnetic plasma waves in dark energy cosmology

TL;DR

This paper investigates electromagnetic wave modes in a dark energy-dominated cosmological plasma, revealing exact solutions and conditions for wave existence influenced by the universe's expansion and plasma thermodynamics.

Contribution

It provides exact solutions for electromagnetic plasma waves in dark energy cosmology and identifies conditions for mode discretization based on initial conditions.

Findings

Exact solutions for cold and hot plasma wave modes using Airy and Bessel functions.

Wave mode discretization depends on initial conditions and plasma thermodynamics.

Only specific electromagnetic modes can exist in this dark energy cosmological setting.

Abstract

We explore electromagnetic wave modes that can exist in a cosmological plasma dominated by dark energy due to a cosmological constant. It is found that, in the cold and hot plasma cases, electromagnetic plasma wave modes can be found exactly. The effect of this cosmology appears as a time-dependent potential in the wave equation for the electromagnetic modes, that effectively modify the frequency response of the plasma. This potential depends on the metric of the spacetime and on the thermodynamical properties of the plasma. For both cases, cold and hot, the solutions are found in terms of Airy and Bessel functions, respectively. When those solutions are required to have vanishing initial conditions, a discretization on the wavelengths of the electromagnetic plasma waves is imposed. Thus, only some specific wave modes can exist in this dark energy cosmology. Relaxing those conditions, we obtain other solutions that approximate to plane waves only in the very hot plasma limit.