Magnetogenesis by non-minimal coupling to gravity in the Starobinsky inflationary model

Savchenko, Oleg; Shtanov, Yuri

doi:10.1088/1475-7516/2018/10/040

Cited by 20 publications

(18 citation statements)

References 35 publications

(62 reference statements)

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“…One may argue that in Ref. [47] the authors show magnetogenesis is not possible because of the strong back reaction of the produced fields on the inflation.…”

Section: Discussionmentioning

confidence: 99%

“…The reason for back-reaction problem in Ref. [47] is, the form of potential due to flatness of the Starobinsky potential. Due to flatness of Starobinsky potential ,the coupling function changes very slowly during inflation so that the form of the power spectrum of electromagnetic field in the amplification domain is not essentially modified with respect to to the vacuum case [47].…”

Section: Discussionmentioning

confidence: 99%

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Magnetogenesis in Higgs inflation

Kamarpour

2021

Gen Relativ Gravit

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We study the generation of magnetic fields in the Higgs inflation model with the axial coupling in order to break the conformal invariance of the Maxwell action and produce strong enough magnetic fields for observed large-scale magnetic fields. This interaction breaks the parity and enables a production of only one of the polarization states of the electromagnetic field due to axion-like coupling of electromagnetic field to the inflation. Therefore, the produced magnetic fields are helical. In fact,calculations show the mode of one polarization undergoes amplification, while the other one diminishes. We consider radiatively corrected Higgs inflation potential. In comparison to the Starobinsky potential, we obtain an extra term as a one loop correction and determine the spectrum of generalized electromagnetic fields. The effect of quantum correction modifies potential so that in some certain conditions when back reaction is weak the observed large-scale magnetic field can be explained by our modified potential. We should emphasize in this model we only consider linear approximation for electromagnetic field so that the theory does not contain higher-order derivatives and the so-called ghost degrees of freedom. Therefore, the theory is consistent with cosmology. In addition,the magnetic field generated in this model has very small correlation length. It is impossible to explain within this model both the strength of magnetic field and its large coherence length. Due to the nontrivial helicity, the produced magnetic fields undergo the inverse cascade process in the turbulent plasma which can strongly increase their correlation length. We find that, for two values of coupling parameter χ 1 = 5×10 9 M −2 p and χ 1 = 7.5×10 9 M −2 p , the back-reaction is weak and our analysis is valid.

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“…One may argue that in Ref. [47] the authors show magnetogenesis is not possible because of the strong back reaction of the produced fields on the inflation.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Magnetogenesis in Higgs inflation

Kamarpour

2021

Gen Relativ Gravit

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“…Moreover, the backreaction of EM fields can modify the inflaton dynamics, change the Universe expansion, and make an impact on the spectrum of primordial perturbations. In our previous work [38], we considered the case of kinetic coupling between the scalar inflaton field and the EM field introduced by Ratra [33] and revisited many times in the literature arXiv:1907.10443v2 [astro-ph.CO] 19 Sep 2019 [37,[39][40][41][42][43][44][45][46][47] and showed that the backreaction of generated electric fields is indeed very important because it strongly suppresses magnetogenesis.…”

Section: Introductionmentioning

confidence: 99%

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

2019

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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 ∼ ( √ 2 /β)ρ inf ( 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 ρE ∼ α −3 EM (ρ 2 tot /M 4 p ), where ρtot = 3H 2 M 2 p 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.

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“…whereF μν = 1 2 μν αβ F αβ is the Hodge dual of the electromagnetic strength tensor F μν , and I and f are non-trivial functions of the cosmological time due to their possible dependence on the background fields such as the inflaton or the metric curvature. In [43], we have shown how such coupling between the curvature and inflaton can arise as a result of quantum corrections in the Starobinsky inflationary model [55]. But we will not specify such couplings here, making our consideration general and model independent.…”

Section: Introductionmentioning

confidence: 99%