Homogeneous and isotropic cosmologies with nonlinear electromagnetic radiation

Dan N. Vollick

doi:10.1103/PhysRevD.78.063524

paper

Homogeneous and isotropic cosmologies with nonlinear electromagnetic radiation

arXiv:0807.0448 · doi:10.1103/PhysRevD.78.063524

Abstract

In this paper I examine cosmological models that contain a stochastic background of nonlinear electromagnetic radiation. I show that for Born-Infeld electrodynamics the equation of state parameter, $w = P / ρ$ , remains close to 1/3 throughout the evolution of the universe if $E^{2} = B^{2}$ in the late universe to a high degree of accuracy. Theories with electromagnetic Lagrangians of the form $L = - 1/4 F^{2} + α F^{4}$ have recently been studied in magnetic universes, where the electric field vanishes. It was shown that the $F^{4}$ term can produce a bounce in the early universe, avoiding an initial singularity. Here I show that the inclusion of an electric field, with $E^{2} ≃ B^{2}$ in the late universe, eliminates the bounce and the universe "begins" in an initial singularity. I also examine theories with Lagrangians of the form $L = - 1/4 F^{2} - μ^{8} / F^{2}$ , which have been shown to produce a period of late time accelerated expansion in magnetic universes. I show that, if an electric field is introduced, the accelerated phase will only occur if $E^{2} < 3 B^{2}$ .

8 pages, change of title plus minor changes

Homogeneous and isotropic cosmologies with nonlinear electromagnetic radiation

Abstract

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