Bianchi Type I model of universe with customized scale factors

Sarmah, Pranjal; Goswami, Umananda Dev

doi:10.1142/s0217732322501346

Cited by 21 publications

(8 citation statements)

References 65 publications

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“…The question of the relationship between the anisotropy in the Bianchi type I model and the anisotropy in the data of astronomical observations was considered, for example, by Sarmah and Goswami (2022). However, this question is quite complex and not so straightforward.…”

Section: Discussionmentioning

confidence: 99%

The Big Bang could be anisotropic. The case of Bianchi I model

Parnovsky

2023

Class. Quantum Grav.

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We consider an evolution of anisotropic cosmological model on the example of the Bianchi type I homogeneous universe. It is filled by the mixture of matter and dark energy with an arbitrary barotropic equation of state (EoS). The general solution for this case is found and analyzed. A complete list of possible future singularities for this model is given. Some new solution were obtained for a particular EoSs, e.g. for the Bianchi type I ΛCDM homogeneous model.It is shown that all special cases corresponding to different EoSs have common properties, provided that now or at another moment of time the Universe is expanding, and the density of the mixture is positive. Then the evolution always begins with an anisotropic ``Big Bang'' which happened a finite time ago. After that the universe is constantly expanding and in all cases, with rare exceptions, becomes more isotropic. A particularly strong isotropization is associated with the epoch of inflation. After its completion, the expansion of the universe becomes almost isotropic, and this case cannot be distinguished from isotropic by astronomical observations. This fact allows us to consider an anisotropic cosmological model as a possible candidate for the description of the observed Universe despite the isotropic pattern of expansion.

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Section: Discussionmentioning

confidence: 99%

The Big Bang could be anisotropic. The case of Bianchi I model

Parnovsky

2023

Class. Quantum Grav.

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“…where ρ and p are the sum of the mass-energy densities and pressure, respectively, of the matter, radiation, and dark energy contents of the universe. Due to Equation (11), it is natural in the Bianchi type I universe models to define an effective gravitational mass density, ρ G , by…”

Section: Field Equations For the Bianchi Type I Universe Modelsmentioning

confidence: 99%

Anisotropic Generalization of the ΛCDM Universe Model with Application to the Hubble Tension

Grøn

2024

Symmetry

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I deduce an exact and analytic Bianchi type I solution of Einstein’s field equations, which generalizes the isotropic ΛCDM universe model to a corresponding model with anisotropic expansion. The main point of the article is to present the anisotropic generalization of the ΛCDM universe model in a way suitable for investigating how anisotropic expansion modifies observable properties of the ΛCDM universe model. Although such generalizations of the isotropic ΛCDM universe model have been considered earlier, they have never been presented in this form before. Several physical properties of the model are pointed out and compared with properties of special cases, such as the isotropic ΛCDM universe model. The solution is then used to investigate the Hubble tension. It has recently been suggested that the cosmic large-scale anisotropy may solve the Hubble tension. I consider those earlier suggestions and find that the formulae of these papers lead to the result that the anisotropy of the cosmic expansion is too small to solve the Hubble tension. Then, I investigate the problem in a new way, using the exact solution of the field equations. This gives the result that the cosmic expansion anisotropy is still too small to solve the Hubble tension in the general Bianchi type I universe with dust and LIVE (Lorentz Invariant Vacuum Energy with a constant energy density, which is represented by the cosmological constant) and anisotropic expansion in all three directions—even if one neglects the constraints coming from the requirement that the anisotropy should be sufficiently small so that it does not have any significant effect upon the results coming from the calculations of the comic nucleosynthesis during the first ten minutes of the universe. If this constraint is taken into account, the cosmic expansion anisotropy is much too small to solve the Hubble tension.

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“…Here H 0 is the current Hubble parameter, Ω m0 = 8πρ m0 /3H 2 0 is the density parameter for the matter content, Ω r0 = 8πρ r0 /3H 2 0 is the density parameter for the radiation content, Ω Λ0 = Λ/3H 2 0 is the density parameter for the vacuum energy and Ω σ0 = σ 2 0 /3H 2 0 is the density parameter for the anisotropy of the present Universe [69]. The term ρ m0 and ρ r0 are current values of matter density and radiation density of the Universe respectively.…”

Section: Dark Energy Eos and Other Cosmological Parametersmentioning

confidence: 99%

“…The term ρ m0 and ρ r0 are current values of matter density and radiation density of the Universe respectively. Again, the term σ 2 0 in Ω σ0 is the current value of shear scalar which is related to the shear scalar σ 2 by the relation σ 2 = σ 2 0 a −6 and Ω σ0 ≤ 10 −15 [69,70].…”

Section: Dark Energy Eos and Other Cosmological Parametersmentioning

confidence: 99%

A Checklist of Orchids Inside Dibrugarh University Campus, Assam, North-East India

Sarmah¹,

Swargiari²,

Hojaisa³

2023

EEC

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Widespread, ornamentally valuable angiosperm orchids belong to the family Orchidaceae. The Dibrugarh University campus is rich in biodiversity. Therefore, a survey was conducted inside the 500 acres area of the university to know the orchid diversity inside the campus. The campus bears 22 different orchid species belonging to 17 genera. The presence of two rear species like Dendrobium nobile and Vanda bicolour was reported from the campus. The campus provides a habitat for endangered species like Aerides odorata. Dendrobium and Cymbidium are the two dominant genera from the campus. The campus holds 17% of total species found all over the Dibrugarh district and 6% of species found in Assam. The species found inside the campus are economically important as they can be used as medicine, food and ornamentally. Although the university has a healthy environment for orchids still, they need more scientific methods and strategies to be developed for their conservation.

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Bianchi Type I model of universe with customized scale factors

Cited by 21 publications

References 65 publications

The Big Bang could be anisotropic. The case of Bianchi I model

The Big Bang could be anisotropic. The case of Bianchi I model

Anisotropic Generalization of the ΛCDM Universe Model with Application to the Hubble Tension

A Checklist of Orchids Inside Dibrugarh University Campus, Assam, North-East India

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