The anisotropy of a three- and a one-form

Urban, Federico R.

doi:10.1088/1475-7516/2013/08/008

Cited by 5 publications

(6 citation statements)

References 33 publications

(51 reference statements)

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“…For instance, a time-dependent interaction between the inflaton and the vector fields can induce non-Gaussian cross-correlations between the metric/curvature perturbations and magnetic fields which turn out to be large for a particular shape and could have interesting cosmological consequences [25][26][27][28][29][30]. Furthermore, statistically anisotropic contribution to the primordial curvature perturbation during inflation as well as anisotropic power spectrum and bispectrum due to the presence of this coupling have also been explored [31][32][33][34].…”

Section: Contentsmentioning

confidence: 99%

Inflationary magnetogenesis without the strong coupling problem

Ferreira

Jain

Sloth

2013

J. Cosmol. Astropart. Phys.

131

158

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The simplest gauge invariant models of inflationary magnetogenesis are known to suffer from the problems of either large backreaction or strong coupling, which make it difficult to self-consistently achieve cosmic magnetic fields from inflation with a field strength larger than 10 −32 G today on the Mpc scale. Such a strength is insufficient to act as seed for the galactic dynamo effect, which requires a magnetic field larger than 10 −20 G. In this paper we analyze simple extensions of the minimal model, which avoid both the strong coupling and back reaction problems, in order to generate sufficiently large magnetic fields on the Mpc scale today. First we study the possibility that the coupling function which breaks the conformal invariance of electromagnetism is non-monotonic with sharp features. Subsequently, we consider the effect of lowering the energy scale of inflation jointly with a scenario of prolonged reheating where the universe is dominated by a stiff fluid for a short period after inflation. In the latter case, a systematic study shows upper bounds for the magnetic field strength today on the Mpc scale of 10 −13 G for low scale inflation and 10 −25 G for high scale inflation, thus improving on the previous result by 7-19 orders of magnitude. These results are consistent with the strong coupling and backreaction constraints.

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Section: Contentsmentioning

confidence: 99%

Inflationary magnetogenesis without the strong coupling problem

Ferreira

Jain

Sloth

2013

J. Cosmol. Astropart. Phys.

131

158

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“…The interesting feature is in the spectral shape: the unphysical isotropic spectrum has a different slope (in this case, shallower) than the physical anisotropic one. We expect this to be the case in general scenarios -this indeed happens in [4,17]. Thus, the isotropic spectrum not only misses the angular dependence of the physical result, but also misleads in terms of the general structure with momentum.…”

Section: Remarksmentioning

confidence: 80%

“…The gauge field fluctuations are boosted exponentially through the coupling with the background; however, this exponential amplification is not very efficient, mostly because the coupling itself is active only just around horizon crossing, and it is not a time-exponential enhancement (see for example [17] for an example of the latter possibility). As always in this kind of chiral couplings, of the two physical helicities of a massless U (1) field, only one is amplified, the second one being instead suppressed.…”

Section: The Correlatorsmentioning

confidence: 99%

Pseudoscalar N-flation and axial coupling revisited

Urban

2013

Phys. Rev. D

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We revisit the dynamics of the axial coupling between many N-flatons and an Abelian gauge field, with special attention to its statistically anisotropic signal. The anisotropic power spectrum of curvature perturbations associated to the large wavelength modes of the gauge vector field is generally undetectable, since the anisotropy is confined to small scales. If the gauge field is the electromagnetic field, provided that the number of fields participating in the exponential expansion is large, it could be possible to generate sizable large scale magnetic fields. However, its spectrum is blue, and appreciable power on large scales implies an overly strong field on smaller scales, incompatibly with observations. Furthermore, the anisotropy is also markedly enhanced, and might be at odds with the isotropic observed sky. These aspects further demand that the scale of inflation is kept to a minimum.Comment: 14 pages - v2 with minor changes in the conclusions, v3 to match published versio

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“…Several models have been already proposed in the literature to break the conformal invariance of the electromagnetic action, as those including a non-trivial coupling between a scalar field (generally considered as the inflaton) and the gauge field [50][51][52][53][54][55]. Alternative scenarios to break the conformal invariance have been proposed in the shelter of non-linear electrodynamics [56] or 3-form fields [57]. Other important issues that affect inflationary magnetogenesis models are the backreaction and the strong coupling problems [10,16,36,51,55,58].…”

Section: Introductionmentioning

confidence: 99%

Inflationary magnetogenesis with reheating phase from higher curvature coupling

Bamba

Elizalde

Odintsov

et al. 2021

J. Cosmol. Astropart. Phys.

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We investigate the generation of helical magnetic fields and address the baryon asymmetry of the universe from an inflationary magnetogenesis scenario, in which the conformal and parity symmetries of the electromagnetic field are broken through its coupling the Ricci scalar and the Gauss-Bonnet invariant via the dual field tensor, so that the generated magnetic field can have a helical nature. It is demonstrated that if a reheating phase with non-zero e-fold numbers following inflation is taken into account, the energy density of the magnetic fields as well as their helicity spectrum evolve differently compared to those for the instantaneous reheating case. As a result, it is shown that in presence of the reheating phase, both the field strength of the generated magnetic fields and the resultant baryon asymmetry of the universe can be compatible with the observations. Furthermore, we find a viable constraint on the reheating equation of state parameter ω eff from the data of the cosmic microwave background radiation as 0.284 ω eff 0.2975, which is consistent with a negligible Schwinger backreaction.

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The anisotropy of a three- and a one-form

Cited by 5 publications

References 33 publications

Inflationary magnetogenesis without the strong coupling problem

Inflationary magnetogenesis without the strong coupling problem

Pseudoscalar N-flation and axial coupling revisited

Inflationary magnetogenesis with reheating phase from higher curvature coupling

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