Perturbations in electromagnetic dark energy

TL;DR

This paper investigates a cosmological model where a temporal electromagnetic field acts as dark energy, producing accelerated expansion similar to DM, and examines whether its perturbations align with observational data.

Contribution

The study analyzes scalar perturbations in electromagnetic dark energy models, demonstrating their compatibility with CMB and large-scale structure observations.

Findings

Electromagnetic perturbations can mimic a cosmological constant without conflicting with observations.

Small initial electromagnetic fluctuations ensure consistency with CMB and structure formation.

The model's predictions are as accurate as DM for current cosmological data.

Abstract

It has been recently proposed that the presence of a temporal electromagnetic field on cosmological scales could explain the phase of accelerated expansion that the universe is currently undergoing. The field contributes as a cosmological constant and therefore, the homogeneous cosmology produced by such a model is exactly the same as that of $\Lambda$CDM. However, unlike a cosmological constant term, electromagnetic fields can acquire perturbations which in principle could affect CMB anisotropies and structure formation. In this work, we study the evolution of inhomogeneous scalar perturbations in this model. We show that provided the initial electromagnetic fluctuations generated during inflation are small, the model is perfectly compatible with both CMB and large scale structure observations at the same level of accuracy as $\Lambda$CDM.