The oscillatory anisotropy in the spatially flat cosmological models

Bizarria, Bruno B.; Silva, Gabriel A. Souza; Gomes, Leandro; Clavijo, William

doi:10.1016/j.aop.2021.168571

Cited by 6 publications

(6 citation statements)

References 33 publications

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“…However, except when γ has constant curvature, it does not satisfy H1. • H1 + H3 + Einstein's equations do not imply H2: any perfect fluid Bianchi I solution of Einstein's equations with Σ = 0 can be used as example (see the general barotropic solution in section 4.1 of [30], for instance). • H1 + H2 +Einstein's equations do not imply H3: for the metric as in corollary 1 with K = 0, any free-falling u-observer is fiducial with Σ = 0.…”

Section: The Three Pieces Of the Cosmological Principlementioning

confidence: 99%

Breaking the cosmological principle into pieces: a prelude to the intrinsically homogeneous and isotropic spacetimes

Gomes

2024

Class. Quantum Grav.

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In this manuscript, we show that there are three fundamental building blocks supporting the Cosmological Principle. The first of them states that there is a special frame in the universe where the spatial geometry is intrinsically homogeneous and isotropic. The second demands the existence of a fiducial observer to whom the Hubble parameter is isotropic. The last piece states that matter and radiation behave as a perfect fluid. We show that these three hypotheses give us the Friedmann-Lemaître-Robertson-Walker (FLRW) spacetimes, the central pillar of the standard model of Cosmology. We keep with the first of them and start to investigate the so-called intrinsically homogeneous and isotropic spacetimes. They emerge after the decoupling of the CMB with the geometric frame of reference. Furthermore, a ``$\Lambda$CDM-like" effective theory arises naturally in those backgrounds, together with some new density parameters relating to the local inhomogeneities, the internal energy density, and the local and global magnitudes of the Hubble anisotropy. All those properties make this class of inhomogeneous models, which roughly speaking, keeps "1/3" of the Cosmological Principle, worth investigating in applications to Cosmology, for it can accommodate the same ingredients of the standard model, as a geometric frame and a free-falling isotropic cosmic background radiation, and reduce to the latter when some observable parameters vanish.

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Section: The Three Pieces Of the Cosmological Principlementioning

confidence: 99%

Breaking the cosmological principle into pieces: a prelude to the intrinsically homogeneous and isotropic spacetimes

Gomes

2024

Class. Quantum Grav.

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“…The authors [50] concluded that the modified structure scalars play an important role in the dynamics of compact object. The authors [51] investigated the oscillatory behaviour of the anisotropy Bianchi -I spacetime. and emphasized the presence of a residue in the energy density in a late time isotropic universe coming from its past anisotropic behaviour.…”

Section: Introductionmentioning

confidence: 99%

A new class of holographic dark energy models in LRS Bianchi Type-I

Pradhan,

Bhardwaj,

Dixit

et al. 2022

Preprint

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In this paper, we examine the (LRS) Bianchi-type-I cosmological model with holographic dark energy. The exact solutions to the corresponding field equations are obtained by using generalized hybrid expansion law (HEL). The EoS parameter ω for DE is found to be time dependent and redshift dependent and its exiting range for derived model is agreeing well with the current observations. Here we likewise apply two mathematical diagnostics, the statefinder (r, s) and ω d − ω ′ d plane to segregate HDE model from the ΛCDM model. Here the ω d − ω ′ d diagnostic trajectories is the good tool to classifying the dynamical DE model. We found that our model lies in both thawing region and freezing region. We have also construct the potential as well as dynamics of the quintessence and tachyon scalar field. Some physical and geometric properties of this model along with the physical acceptability of cosmological solution have been discussed in detail.

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“…The constraints in the theorems 1 and 2 hold not only for the perfect fluid Bianchi-I system, but more than this, also in the late-time spatially flat universe with H bounded (H → ±∞ as t → ∞ does not occur) and N Σ. In fact, the corrections induced in the energy density, and thus in the increment ΔR, the deceleration and the jerk, are of order N Σ Σ 2 , while α ∼ (N H)/Σ H (see the equations for ρ (7), α (11) and Ḣ/H 2 (18) in the reference [15], where η = 2N w, γ = 1 + w and w = p/ρ). For instance, even for Σ 0 1, we would have ΔR ∼ Σ 2 0 , which is far greater than the perturbation N 0 Σ 0 , while δq k ∼ δj k ∼ Σ 0 .…”

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confidence: 99%

“…In each of them, the spacetime anisotropy displays a peculiar behaviour, which in most cases are far beyond the standard picture of an ever decreasing parameter. The examples in the reference [15] give us a glimpse of how vast are the possibilities for the time evolution of Σ in the Kasner disc. It is remarkable that the condition Σ → 0 as t → ∞ in conjunction with the hypothesis that the universe has been very homogeneous and isotropic at some point in the past, as at the end of the inflationary era, for example, is possible only for a set of measure zero in the space of the spatially homogeneous initial conditions, according to a theorem by Collins and Hawking [16].…”

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confidence: 99%

“…Moreover, it is compatible with an early isotropic period (Σ → 0 as t → 0) while all the others parameters are kept in the most acceptable physical region 3 . In the spatially flat case, at least, as we use the theorem 2-(iii) and the formula (11) in the reference [15] (η = 2N w, γ = 1 + w and w = p/ρ), we must have α → 0 as t → ∞, which is equivalent to (wH(1 − Σ 2 )N sin β)/Σ → 0. In particular, if we have a late time dominance of the cosmological constant (wH → 0 does not happen) with the asymptotic anisotropy not approaching its maximum value (Σ → 1 does not happen) and sin β does not tending to 0, then we must have N → 0 with Σ > Σ c > 0, filling our conditions for the applicability of the theorems 1 and 2.…”

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confidence: 99%

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The nonlinear patterns of the cosmic anisotropy: the spatially flat perfect fluid universes

Gomes¹

2021

Class. Quantum Grav.

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In this manuscript, we investigate the patterns of the cosmological anisotropy in the spatially flat Bianchi models filled with a perfect fluid. We analyse the factor 1 + ∆R, the ratio of the Hubble parameter in the anisotropic model over its isotropic counterpart. In general, ∆R starts to deviate significantly from zero at a specific redshift zA, which depends on the type of the fluid and the value of the anisotropy magnitude. We also show that the deceleration and the jerk along the principal directions of the expansion tensor are constrained by simple algebraic equations that do not depend on the type of matter present. These characteristic patterns form a valuable framework to probe the cosmological anisotropy in the late-time universe.

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The oscillatory anisotropy in the spatially flat cosmological models

Cited by 6 publications

References 33 publications

Breaking the cosmological principle into pieces: a prelude to the intrinsically homogeneous and isotropic spacetimes

Breaking the cosmological principle into pieces: a prelude to the intrinsically homogeneous and isotropic spacetimes

A new class of holographic dark energy models in LRS Bianchi Type-I

The nonlinear patterns of the cosmic anisotropy: the spatially flat perfect fluid universes

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