Gauge-invariant magnetic perturbations in perfect-fluid cosmologies

TL;DR

This paper extends a covariant, gauge-invariant formalism to analyze how magnetic fields influence density perturbations in relativistic cosmology, revealing new physical effects during the radiation era.

Contribution

It introduces a detailed framework for studying magnetized cosmological perturbations with pressure, expanding understanding of magnetic effects in early universe models.

Findings

Magnetic fields affect the growth of density irregularities during radiation era.

Solutions for density evolution on various scales in magnetized, pressurized fluids are provided.

New physical effects related to magnetohydrodynamics in cosmological perturbations are identified.

Abstract

We develop further our extension of the Ellis-Bruni covariant and gauge-invariant formalism to the general relativistic treatment of density perturbations in the presence of cosmological magnetic fields. We present detailed analysis of the kinematical and dynamical behaviour of perturbed magnetized FRW cosmologies containing fluid with non-zero pressure. We study the magnetohydrodynamical effects on the growth of density irregularities during the radiation era. Solutions are found for the evolution of density inhomogeneities on small and large scales in the presence of pressure, and some new physical effects are identified.