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

• Published in: Physical review. D 2019-09, Vol.100 (6), Article 063523
• Main Authors: Sobol, O. O., Gorbar, E. V., Vilchinskii, S. I.
• Format: Article
• Language: English
• Subjects: Charged particles; Coupling; Electromagnetic fields; Flux density; Heating; Quadratic equations; Universe
• ISSN: 2470-0010; 2470-0029
• DOI: 10.1103/PhysRevD.100.063523

We study magnetogenesis in axionlike inflation driven by a pseudoscalar field ϕ coupled axially to the electromagnetic (EM) field (β/Mp)ϕFμνF˜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 ρEM∼(2ε/β)ρinf (ε is the slow-roll parameter and ρinf 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 ρE∼αEM−3(ρtot2/Mp4), where ρtot=3H2Mp2 is the total energy density and αEM 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 10−15  G, however, only with the correlation length of order 1 pc at present.