Linear perturbations of an anisotropic Bianchi I model with a uniform magnetic field

Gioia, Federico Di; Montani, Giovanni

doi:10.1140/epjc/s10052-019-7411-2

Cited by 6 publications

(9 citation statements)

References 37 publications

(86 reference statements)

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“…We now derive the density perturbation evolution equation in general relativistic scenario where we can treat it as a special case of our more general result by substituting f (R) = 0 in (1) and subsequent equations. Therefore, from (38) we obtain in the GR case…”

Section: Evolution Equations In the General Relativistic Case And Oth...mentioning

confidence: 98%

“…Note that the higher curvature terms are absent in (46) unlike (38). Consequently with appropriate approximations mentioned in the beginning of this section, equation ( 46) can be expressed as follows:…”

Section: Evolution Equations In the General Relativistic Case And Oth...mentioning

confidence: 99%

“…In [37] the authors extended the standard theory of cosmological perturbations to homogeneous but anisotropic universes using the case of a Bianchi I model, with a residual isotropy between two spatial dimensions, which is undergoing complete isotropization at the onset of inflation. Recently in [38] the authors examined the effect of a magnetic field on the growth of cosmological perturbations by developing a mathematical treatment in which a perfect fluid and a uniform magnetic field evolve together in a Bianchi I universe.…”

Section: Introductionmentioning

confidence: 99%

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Density perturbation and cosmological evolution in the presence of magnetic field in $f(R)$ gravity models

Chakraborty¹,

Guha²

2021

Preprint

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In this paper, we have investigated the density perturbations and cosmological evolution in the FLRW universe in presence of a cosmic magnetic field, which may be assumed to mimic primordial magnetic fields. Such magnetic fields have sufficient strength to influence galaxy formation and cluster dynamics, thereby leaving an imprint on the CMB anisotropies. We have considered the FLRW universe as a representative of the isotropic cosmological model in the 1+3 covariant formalism for f (R) gravity. The propagation equations have been determined and analyzed, where we have assumed that the magnetic field is aligned uniformly along the x-direction, resulting in a diagonal shear tensor. Subsequently,the density perturbation evolution equations have been studied and the results have been interpreted. We have also indicated how these results change in the general relativistic case and briefly mentioned the expected change in higher-order gravity theories.

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Section: Evolution Equations In the General Relativistic Case And Oth...mentioning

confidence: 98%

Section: Evolution Equations In the General Relativistic Case And Oth...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Density perturbation and cosmological evolution in the presence of magnetic field in $f(R)$ gravity models

Chakraborty¹,

Guha²

2021

Preprint

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“…(10d). On the other hand, the magnetic Jeans length, calculated in [24], is about 10 Mpc −1 and is a much more stringent constraint.…”

mentioning

confidence: 98%

“…Afterwards, we still use it as a conservative choice, overestimating the viscous damping. For solutions with z < 100 and in the absence of viscosity, see [12,24].…”

mentioning

confidence: 99%

On the influence of viscosity on the anisotropic dynamics of cosmological perturbations in the presence of a magnetic field

Gioia¹,

Incarbone²,

Montani³

2021

EPL

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We analyse the influence that viscous effects can induce on the evolution of primordial perturbations to the isotropic universe in the presence of a weak uniform magnetic field. Previous analyses have shown that the presence of the magnetic field induces an intrinsic anisotropy in the perturbations dynamics, essentially because of the anisotropic character of the perturbed magnetic pressure. This anisotropic effect is of order unity in the perturbation amplitude, although it remains small in the linear theory when the density constraints are considered. The aim of this study is to determine the impact of viscosity, surely present in the early universe, on the growth of the perturbation anisotropy. The main merit of this study consists of demonstrating that a tiny overlapping exists in the parameter space to deal simultaneously with anisotropic features due to the magnetic field and the viscous damping of such density fluctuation. Actually, we demonstrate that the viscosity affects the value of the anisotropy, by smoothing the growing rate of the instability only when structure smaller than about 5000 solar masses are concerned. This result allows us to guarantee that the intrinsic anisotropy of the magnetized universe perturbations is not affected by the viscosity due to friction among inhomogeneous layers or compressive-like effects, and therefore, they remain good candidates for being seeds for filament formation across the universe.

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Opening of New Windows to the Early Universe by Means of Multi-Messenger Astronomy (Brief Review)

Arbuzova,

Dolgikh,

Dolgov

et al. 2024

Jetp Lett.

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Linear perturbations of an anisotropic Bianchi I model with a uniform magnetic field

Cited by 6 publications

References 37 publications

Density perturbation and cosmological evolution in the presence of magnetic field in $f(R)$ gravity models

Density perturbation and cosmological evolution in the presence of magnetic field in $f(R)$ gravity models

On the influence of viscosity on the anisotropic dynamics of cosmological perturbations in the presence of a magnetic field

Opening of New Windows to the Early Universe by Means of Multi-Messenger Astronomy (Brief Review)

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