Magnetogenesis during inflation and preheating in the Starobinsky model

Vilchinskiĭ, S. I.; Sobol, O. O.; Gorbar, É. V.; Rudenok, Igor

doi:10.1103/physrevd.95.083509

Cited by 31 publications

(39 citation statements)

References 78 publications

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“…For decreasing coupling functions, it is well known that the electric energy density dominates the magnetic one [39,40,44] and if we try to generate the magnetic field strong enough to be in accord with the observations, the electric field appears to be even stronger and its energy density exceeds that of the inflaton field. This is known as the backreaction problem.…”

Section: Introductionsupporting

confidence: 55%

Influence of backreaction of electric fields and Schwinger effect on inflationary magnetogenesis

et al. 2018

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We study the generation of electromagnetic fields during inflation when the conformal invariance of Maxwell's action is broken by the kinetic coupling f 2 (φ)FµνF µν of the electromagnetic field to the inflaton field φ. We consider the case where the coupling function f (φ) decreases in time during inflation and, as a result, the electric component of the energy density dominates over the magnetic one. The system of equations which governs the joint evolution of the scale factor, inflaton field, and electric energy density is derived. The backreaction occurs when the electric energy density becomes as large as the product of the slow-roll parameter ǫ and inflaton energy density, ρE ∼ ǫρ inf . It affects the inflaton field evolution and leads to the scale-invariant electric power spectrum and the magnetic one which is blue with the spectral index nB = 2 for any decreasing coupling function. This gives an upper limit on the present-day value of observed magnetic fields below 10 −22 G. It is worth emphasizing that since the effective electric charge of particles e eff = e/f is suppressed by the coupling function, the Schwinger effect becomes important only at the late stages of inflation when the inflaton field is close to the minimum of its potential. The Schwinger effect abruptly decreases the value of the electric field, helping to finish the inflation stage and enter the stage of preheating. It effectively produces the charged particles, implementing the Schwinger reheating scenario even before the fast oscillations of the inflaton. The numerical analysis is carried out in the Starobinsky model of inflation for the powerlike f ∝ a α and Ratra-type f = exp(βφ/Mp) coupling functions.

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Section: Introductionsupporting

confidence: 55%

Influence of backreaction of electric fields and Schwinger effect on inflationary magnetogenesis

et al. 2018

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“…The inflationary and slow-roll parameters are given by 15) and the inflationary and slow-roll conditions ǫ V ≪ 1 and η V ≪ 1 are both satisfied if e φ/M ≫ 1. In this regime, we have 16) and the slow-roll dynamics (2.13) is described bẏ…”

Section: Inflationary Regimementioning

confidence: 99%

“…The quantities I 2 ± (η) will be assumed to be always positive, in order to avoid instability. 15) and integrating by part in (3.13), we obtain the action 16) and the equation of motion for the Fourier mode of v i with wavenumber k :…”

Section: Lagrangianmentioning

confidence: 99%

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

Savchenko¹,

Shtanov²

2018

J. Cosmol. Astropart. Phys.

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The R 2 term in the Starobinsky inflationary model can be regarded as a leading quantum correction to the gravitational effective action. We assume that parity-preserving and parity-violating (axial) non-minimal couplings between curvature and electromagnetic field are also present in the effective action. In the Einstein frame, they turn into non-trivial couplings of the scalaron and curvature to the electromagnetic field. We make an assessment of inflationary magnetogenesis in this model. In the case of parity-preserving couplings, amplification of magnetic field is negligibly small. In the case of axial couplings, magnetogenesis is hampered by strong back-reaction on the inflationary process, resulting in possible amplification of magnetic field at most by the factor 10 5 relative to its vacuum fluctuations.

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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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Magnetogenesis during inflation and preheating in the Starobinsky model

Cited by 31 publications

References 78 publications

Influence of backreaction of electric fields and Schwinger effect on inflationary magnetogenesis

Influence of backreaction of electric fields and Schwinger effect on inflationary magnetogenesis

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

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

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