Some Homogeneous Bianchi type IX Viscous Fluid Cosmological Models with a Varying Λ

Pradhan, Anirudh; Srivastav, Sudhir Kumar; Yadav, Mahesh Kumar

doi:10.1007/s10509-005-5832-x

Cited by 18 publications

(13 citation statements)

References 48 publications

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“…From a geometrical perspective, anisotropic cosmological models, including the so-called Bianchi cosmologies are the main candidates to explain the intrinsic anisotropy of the universe (see for e.g. Russell et al 2013;Pradhan et al 2005Petzold 1989Kim and Kawai 2013;Pradhan 2013;Bronnikov et al 2004;Singh and Ewing 2014;Corichi and Montoya 2012;Yadav and Saha 2012;Sepehri et al 2014;Amirhashchi and Pradhan 2014;Mishra et al 2013). …”

Section: Introductionmentioning

confidence: 99%

Cosmic acceleration and varying alpha in anisotropic universe

Farajollahi

Tayebi

2015

Astrophys Space Sci

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Recent observational constraints from the Planck and Wilkinson Microwave Anisotropy Probe (WMAP) indicate tiny temperature anisotropies and some large angle anomalies in the Cosmic Microwave Background (CMB). These anisotropies may originated from an anisotropic geometric background, the matter distribution or both. In this paper we assume a homogeneous and anisotropic Bianchi type-I universe subject to variation of the fine structure constant, α, in the Bekenstein-Sandvik-BarrowMagueijo (BSBM) theory (Sandvik et al. in Phys. Rev. Lett. 88:031302, 2002). By performing stability analysis, the anisotropic cosmic attractors are studied. The outcome confirms small anisotropies in an accelerating cosmic expansion. The result also predicts a larger variation of fine structure constant in an decelerating universe in future.

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Section: Introductionmentioning

confidence: 99%

Cosmic acceleration and varying alpha in anisotropic universe

Farajollahi

Tayebi

2015

Astrophys Space Sci

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“…Next, we assume that the coefficient of shear viscosity (η) is proportional to the expansion scalar (θ ), i.e., η ∝ θ , which leads to (see, Pradhan et al 2005;Pradhan and Pandey 2006;Singh and Chaubey 2007) …”

Section: Solution Of Field Equationsmentioning

confidence: 99%

Viscous fluid cosmology with a cosmological constant

Singh

Kumar

2009

Astrophys Space Sci

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Exact solutions of the field equations for a Bianchi type-I space-time, filled with a viscous fluid and cosmological constant, are obtained. We utilize the constancy of deceleration parameter to get singular and non-singular solutions. We investigate a number of solutions with constant and time-varying cosmological constant together with a linear relation between shear viscosity and expansion scalar. Due to dissipative processes, the mean anisotropy and shear of the model tend to zero at a faster rate.

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“…Pradhan [4] have studied some homogeneous Bianchi type-IX viscous fluid cosmological model with varying cosmological constant. On the other hand, Bulk viscosity plays a significant role in the early evolution of the universe and contributes to the accelerated expansion phase of the universe popularly known as the inflationary phase.…”

Section: Introductionmentioning

confidence: 99%

Bianchi Type IX Magnetized Bulk Viscous String Cosmological Model in General Relativity

Mete¹,

Elkar²,

Deshmukh³

2017

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Abstract. In this paper we present a bulk viscous magnetized Bianchi type IX string cosmological model in general relativity. In order to find determinate solution of the investigated model, we assume the conditions :(i) Scalar expansion is proportional to shear scalar and (ii) ξθ = constant, where ξ is bulk viscosity and θ is scalar expansion. Some physical and geometrical properties of the investigated model are also discussed. Keywords:Bianchi type IX space time, bulk viscous, magnetized cosmic string. IntroductionIt is well known that Einstein's general theory of relativity has been successful in finding different models for the universe. Einstein's theory of general relativity is considered as the only successful theory of gravitation in terms of geometry which has the most beautiful structure of the theoretical physics. In recent years, Bianchi type-IX cosmological models are very popular for relativistic studies. These models are also used to examine the role of certain anisotropic sources during the formation of large scale structure as we see the universe today. Many researchers have taken keen interest in studying Bianchi Type IX universes, because familiar solutions like Robertson Walker universe with positive curvature, the de-Sitter universe, the Taub On the other hand, Bulk viscosity plays a significant role in the early evolution of the universe and contributes to the accelerated expansion phase of the universe popularly known as the inflationary phase. The effect of viscosity on the evolution of cosmological models and the role of viscosity in avoiding the initial big bang singularity have been studied by several authors [5][6]. In late nineties, two teams studying distant type Ia-supernovae (SNe-Ia) independently presented evidence of expansion [7][8] and confirmed later by cross checks from the cosmic microwave background radiation (CMBR) [9] and large scale structure (LSS) [10][11][12][13].In addition, the magnetic field has important role at the cosmological scale and is present in galactic and intergalactic space. It plays a vital role in the description of the energy distribution in the universe as it contains highly ionized matter. Strong magnetic fields can be created due to adiabatic compression in cluster of galaxies. Large scale magnetic fields give rise to anisotropies in the universe. Primordial magnetic fields of cosmological origin have been discussed by Asseo et.al [14] and Madsen [15]. Melvin [16] suggested, in the cosmological solution for dust and electromagnetic fields, that during the evolution of the universe, the matter was in highly ionized state and smoothly coupled with electromagnetic and consequently formed a neutral matter as a result of expansion of the universe. Hence, in a string dust universe the presence of magnetic fields is not unrealistic. The magnetic field has the significant role in the dynamics of the universe depending on the direction of the field lines [17][18]

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Some Homogeneous Bianchi type IX Viscous Fluid Cosmological Models with a Varying Λ

Cited by 18 publications

References 48 publications

Cosmic acceleration and varying alpha in anisotropic universe

Cosmic acceleration and varying alpha in anisotropic universe

Viscous fluid cosmology with a cosmological constant

Bianchi Type IX Magnetized Bulk Viscous String Cosmological Model in General Relativity

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