Some Exact Bianchi Type-V Perfect Fluid Cosmological Models with Heat Flow and Decaying Vacuum Energy Density Λ: Expressions for Some Observable Quantities

Pradhan, Anirudh; Jotania, Kanti

doi:10.1007/s10773-010-0352-z

Cited by 18 publications

(13 citation statements)

References 100 publications

(135 reference statements)

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“…Such type of relations have already been considered by Berman and Gomide [84] for solving FRW models. Latter on many authors (see, Saha and Rikhvitsky [85], Saha [86], Singh et al [87], Singh and Chaubey [88,89], Zeyauddin and Ram [90], Singh and Baghel [91], Pradhan and Jotania [92] and references therein) have studied flat FRW and Bianchi type models by using the special law for Hubble parameter that yields constant value of deceleration parameter. From (18) and (19), we get…”

Section: Solutions Of the Field Equationsmentioning

confidence: 99%

Anisotropic Bianchi Type-I String Cosmological Models in Normal Gauge for Lyra’s Manifold with Constant Deceleration Parameter

Pradhan

Singh

2010

Int J Theor Phys

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The present study deals with a spatially homogeneous and anisotropic Bianchi type-I (B-I) cosmological models representing massive strings in normal gauge for Lyra's manifold by applying the variation law for generalized Hubble's parameter that yields a constant value of deceleration parameter. The variation law for Hubble's parameter generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential-law type. Using these two forms, Einstein's modified field equations are solved separately that correspond to expanding singular and non-singular models of the universe respectively. The energy-momentum tensor for such string as formulated by Letelier, P.S.: Phys. Rev. D 28, 2414 is used to construct massive string cosmological models for which we assume that the expansion (θ ) in the model is proportional to the component σ 1 1 of the shear tensor σ j i . This condition leads to A = (BC) m , where A, B and C are the metric coefficients and m is proportionality constant. Our models are in accelerating phase which is consistent to the recent observations. It has been found that the displacement vector β behaves like cosmological term in the normal gauge treatment and the solutions are consistent with recent observations of SNe Ia. It has been found that massive strings dominate in the both decelerating and accelerating universes. The strings dominate in the early universe and eventually disappear from the universe for sufficiently large times. This is in consistent with the current observations. Some physical and geometric behaviour of these models are also discussed.

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Section: Solutions Of the Field Equationsmentioning

confidence: 99%

Anisotropic Bianchi Type-I String Cosmological Models in Normal Gauge for Lyra’s Manifold with Constant Deceleration Parameter

Pradhan

Singh

2010

Int J Theor Phys

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“…Such type of relations have already been considered by Berman [119], Berman and Gomide [120] for solving FRW models. Latter on many authors (see, Singh et al [121][122][123], Pradhan and Jotania [124] and references (10) and (16), we get (17) and (18) Substituting (17) and (18) into (12), we get (19) We observe that the relation (19) gives q as a constant. The sign of q indicates whether the model inflates or not.…”

Section: Bianchi Type I Anisotropic Dark Energy Modelsmentioning

confidence: 73%

Accelerating dark energy models of the universe in anisotropic Bianchi type space-times and recent observations

Pradhan

Saha

2015

Phys. Part. Nuclei

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Motivated by the increasing evidence for the need of a geometry that resembles Bianchi morphol ogy to explain the observed anisotropy in the WMAP data, we have discussed some features of the Bianchi type universes in the presence of a fluid that wields an anisotropic equation of state (EoS) parameter in gen eral relativity. Such models are of great interest in cosmology in favor of constructing more realistic models than FLRW models with maximally symmetric spatial geometry. Additionally, the interest in such models was promoted in recent years due to the debate that going on the analysis and the interpretation of the WMAP [21,111,112] data, whether they need a Bianchi type morphology to be explained successfully [7,103,118,117]. The LLC-WMAP data maps show seven axes well aligned with one another and the direction Virgo. For this reason Bianchi models are important in the study of anisotropies. In the present study of Bianchi type I, II, III, V and VI 0 space times, we observe that the EoS for dark energy ω is found to be time dependent and its existing range for derived models is in good agreement with the recent observations of SNe Ia data [50], SNe Ia data with CMBR anisotropy and galaxy clustering statistics [11] and latest combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift type Ia supernovae and galaxy clustering [21,51]. It has been suggested that the dark energy that explains the observed accelerating expan sion of the universe may arise due to the contribution to the vacuum energy of the EoS in a time dependent background. The cosmological constant Λ is found to be a positive decreasing function of time and it approaches to a small positive value at late time (i.e. the present epoch) which is corroborated by results from recent type Ia supernovae observations.

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“…Such type of relations have firstly been considered by Berman and Gomide [88] for solving FRW models. Latter on many authors (see, Saha and Rikhvitsky [89], Saha [90], Singh et al [91], Singh and Chaubey [92,93], Zeyauddin and Ram [94], Singh and Baghel [95], Pradhan and Jotania [96] and references therein) have studied flat FRW and Bianchi type models by using the special law for Hubble parameter that yields constant value of deceleration parameter. From (25) and (26), we get…”

Section: Solutions Of the Field Equationsmentioning

confidence: 99%

Magnetized String Cosmology in Anisotropic Bianchi-II Space-time with Variable Cosmological Term-Λ

Jotania

Yadav²,

Faruqi³

2011

Int J Theor Phys

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The present study deals with a spatially homogeneous and anisotropic Bianchi-II cosmological models representing massive strings by applying the variation law for generalized Hubble's parameter that yields a constant value of deceleration parameter. We find that the constant value of deceleration parameter is reasonable for the present day universe. The variation law for Hubble's parameter generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential form. Using these two forms, Einstein's field equations are solved separately that correspond to expanding singular and non-singular models of the universe respectively. The energy-momentum tensor for such string as formulated by Letelier (Phys. Rev. D 28:2414) is used to construct massive string cosmological models for which we assume that the expansion (θ ) in the model is proportional to the component σ 1 1 of the shear tensor σ j i . This condition leads to A = (BC) m , where A, B and C are the metric coefficients and m is proportionality constant. Our models are in accelerating phase which is consistent to the recent observations. The cosmological constant is found to be a decreasing function of time and it approaches a small positive value at present epoch which is in good agreement by the results from recent supernovae observations. Some physical and geometric behaviour of the models are also discussed.

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Some Exact Bianchi Type-V Perfect Fluid Cosmological Models with Heat Flow and Decaying Vacuum Energy Density Λ: Expressions for Some Observable Quantities

Cited by 18 publications

References 100 publications

Anisotropic Bianchi Type-I String Cosmological Models in Normal Gauge for Lyra’s Manifold with Constant Deceleration Parameter

Anisotropic Bianchi Type-I String Cosmological Models in Normal Gauge for Lyra’s Manifold with Constant Deceleration Parameter

Accelerating dark energy models of the universe in anisotropic Bianchi type space-times and recent observations

Magnetized String Cosmology in Anisotropic Bianchi-II Space-time with Variable Cosmological Term-Λ

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