Viable inflationary magnetogenesis with helical coupling

Abstract

We consider helical coupling to electromagnetism and present a simple scenario of evolution of the coupling function leading to a viable inflationary magnetogenesis without the problem of back-reaction. In this scenario, helical magnetic fields of strength of order up to 10 −7 G, when extrapolated to the current epoch, can be generated in a narrow spectral band centered at any reasonable wavenumber by adjusting the model parameters. We discuss implications of this model for baryogenesis, which impose additional constraints on the strength and correlation length of magnetic field.

Inflationary Magnetogenesis with Helical Coupling

“…Basing on this observation, we considered in [21] a linear dependence of as a function of conformal time: ′ ( ) = const, 1 ≤ ≤ 2 , joining the time epochs with constant values of . The growth of ℎ in this case is exponential for one of the helicities in the interval 1 < < 2 .…”

“…Back-reaction on inflation and on the dynamics of the inflaton field in the scenario under consideration was estimated in [21] with the upper bound…”

“…Evolution in the form ∝ (log ) during inflation (arising in the case of linear dependence of on the inflaton field) generically leads to maximally helical magnetic fields with blue power spectrum [17][18][19] and with too little power on the comoving scales of galaxies, clusters and voids to account for the magnetic fields in these objects [7]. Evolution in the form of power law ∝ with > 0 [20] also allows for only a negligible amplification of magnetic field [21].…”

Constraints in inflationary magnetogenesis

“…Many models of evolution of I and f were tried in the literature to overcome these difficulties and to obtain the highest possible value of primordial magnetic field. Given the diversity of these approaches, and based on our preliminary studies [49,50], we suggested in [51] to seek for modelindependent constraints imposed by all these limitations for the whole class of models described by (1). This is similar in spirit to the previous studies [10,62], which, however, imposed a priori ansatzes for the evolution of the couplings and did not take into account the Schwinger effect.…”

“…This is similar in spirit to the previous studies [10,62], which, however, imposed a priori ansatzes for the evolution of the couplings and did not take into account the Schwinger effect. Here, we will review the results of our investigation in [49][50][51].…”