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

Gomes, Leandro

doi:10.1088/1361-6382/ac3ae1

Cited by 5 publications

(2 citation statements)

References 26 publications

(44 reference statements)

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“…Last but not least important, the constraints our model imposes on the observational data, in the lines of Ref. [32], is something we have not touched upon in this manuscript. We leave this issue to be accomplished elsewhere.…”

Section: Final Remarksmentioning

confidence: 97%

Spatially flat universes with isotropic tidal forces

Dias¹,

Gomes²,

Mello³

2022

Preprint

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We investigate the dynamics of the spatially flat universes submitted to isotropic tidal forces and adiabatic expansion under Einstein's equations. Surprisingly, the tendency to a high Hubble anisotropy at late times starts to appear as far as we assume the strong energy condition, a characteristic which becomes dominant in the radiation era and even more stringent under a stiff matter regime. We introduce the parameter b which measures the relative change in the magnitudes of the Hubble anisotropy and the scale factor and use it to show that the anisotropies must be kept small as long as we assume the Universe has passed through an inflationary period, in accordance with the cosmic no-hair theorem. Hence, we have a class of models that shows us in a simple and straightforward way the instability of the FLRW universes, the furtiveness of the isotropy concept, and how they can still be consistent with the standard model of Cosmology as far as we assume the occurrence of an inflationary early period.

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Section: Final Remarksmentioning

confidence: 97%

Spatially flat universes with isotropic tidal forces

Dias¹,

Gomes²,

Mello³

2022

Preprint

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“…However, the arguments put above show us that it is possible to have an environment where a ΛCDM-like model naturally coexists with non-linear inhomogeneities and anisotropies, and therefore turns out to be an interesting arena to investigate further the role they play in different phases of the Universe. For instance, we could have a better theoretical framework to analyze whether the isotropy of the CMB [56] and the 'cosmic no-hair' argument [57] are enough to imply the isotropy of the Hubble sky, as it is often believed, against some observational and theoretical arguments (see [4][5][6]58] ). On the other hand, the nonlinear treatment of the inhomogeneities could enhance our knowledge of the events beginning in the time of the last scattering until today and their connection with the CMB observations [59], eventually with new prospects to understand the late-time Hubble tension [60].…”

Section: Towards An Effective Homogeneous Model From 1/3 Of the Cosmo...mentioning

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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Spacetimes with homogeneous and isotropic expansion

Gomes

2024

Class. Quantum Grav.

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

Cited by 5 publications

References 26 publications

Spatially flat universes with isotropic tidal forces

Spatially flat universes with isotropic tidal forces

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

Spacetimes with homogeneous and isotropic expansion

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