Backreaction of electromagnetic fields and the Schwinger effect in pseudoscalar inflation magnetogenesis

O. O. Sobol; E. V. Gorbar; S. I. Vilchinskii

doi:10.1103/PhysRevD.100.063523

paper

Backreaction of electromagnetic fields and the Schwinger effect in pseudoscalar inflation magnetogenesis

arXiv:1907.10443 · doi:10.1103/PhysRevD.100.063523

Abstract

We study magnetogenesis in axionlike inflation driven by a pseudoscalar field $ϕ$ coupled axially to the electromagnetic (EM) field $(β / M_{p}) ϕ F_{μν} F ~^{μν}$ with dimensionless coupling constant $β$ . A set of equations for the inflaton field, scale factor, and expectation values of quadratic functions of the EM field is derived. These equations take into account the Schwinger effect and the backreaction of generated EM fields on the Universe expansion. It is found that the backreaction becomes important when the EM energy density reaches the value $ρ_{EM} \sim (2 ε / β) ρ_{inf}$ ( $ε$ is the slow-roll parameter and $ρ_{inf}$ is the energy density of the inflaton) slowing down the inflaton rolling and terminating magnetogenesis. The Schwinger effect becomes relevant when the electric energy density exceeds the value $ρ_{E} \sim α_{EM}^{- 3} (ρ_{tot}^{2} / M_{p}^{4})$ , where $ρ_{tot} = 3 H^{2} M_{p}^{2}$ is the total energy density and $α_{EM}$ is the EM coupling constant. For large $β$ , produced charged particles could constitute a significant part of the Universe energy density even before the preheating stage. Numerically studying magnetogenesis in the $α$ -attractor model of inflation, we find that it is possible to generate helical magnetic fields with the maximal strength $1 0^{- 15} G$ , however, only with the correlation length of order $1 pc$ at present.

arXiv comment24 pages, 5 figures

Backreaction of electromagnetic fields and the Schwinger effect in pseudoscalar inflation magnetogenesis

Abstract

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