Bianchi Type-IX Anisotropic Dark Energy Cosmological Models with Time Dependent Deceleration Parameter

Bianchi type-IX cosmological models with variable equation of state (EoS) parameter have been investigated in general relativity when universe is filled with dark energy. The field equations have been solved by considering (i) q=B (variable);(ii) , where k and m are constants;(iii) , where k is constant and R is average scale factor;(iv) which gives . This renders early decelerating and late time accelerating cosmological models. The physical and geometrical properties of the models are also discussed.

Energy-Momentum Density of Non-Diagonal Bianchi Type Space-Time in General Relativity and Teleparallel Gravity

We calculated the energy-momentum density of non-diagonal Bianchi type space-time in two different theories of gravity, General relativity (GR) and the theory of Teleparallel gravity (TG). Firstly, by applying Einstein, Landau-Lifshitz, Bergmann-Thomson and Møller prescriptions, using double index complexes in GR. Secondly, in the frame work of TG, we used the energy momentum complexes of Einstein, Bergmann-Thomson and Landau-Lifshitz. We also study the spacial cases of non-diagonal Bianchi type space-time BII, BVIII and BIX. We obtained the same energy-momentum density components for Einstein and Bergmann-Thomson prescriptions for the above four mentioned space-times that we considered in our work. Also, we found that the energy density component in Møller prescription is zero for all Bianchi types space-times in GR. Furthermore, we show that if the metric components are functions of time t alone, then the total gravitational energy is identically zero.

Bianchi Type-I Anisotropic Universe with Metric Potential in Saez-Ballester Theory of Gravitation

Bianchi Type-I cosmological model in the presence of Saez-Ballester theory gravitation is studied. An exact solution of the field equation is given by considering the cosmological model yield a metric potential included with a real number. The relation between the deceleration parameter and Hubble parameter and average scale factor is used in that cosmological model. The effect of the viscosity on the entropy of the universe is utilized by energy momentum tensor with bulk viscous terms in a conservative manner. We obtained a formula for calculating the entropy of the universe in terms of viscosity and used it to compare to the study. Also, various physical and kinematical properties have been discussed.

LRS Bianchi Type-I Cosmological Model with Anisotropic Dark Energy and Special Form of Deceleration Parameter

We have studied Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model filled with anisotropic fluid in general theory of relativity. The solutions of the field equations are obtained by using special form of deceleration parameter which gives early deceleration and late time accelerating cosmological model. The geometrical and physical aspect of the model is also studied.

LRS Bianchi Type-I Universe with Anisotropic Dark Energy in Lyra Geometry

The exact solutions of the Einstein field equations for dark energy (DE) in Locally Rotationally Symmetric (LRS) Bianchi type-I metric under the assumption on the anisotropy of the fluid are obtained for exponential volumetric expansion within the frame work of Lyra manifold for uniform and time varying displacement field. The isotropy of the fluid and space is examined.

Bianchi-Type II String Cosmological Models with Bulk Viscosity

The locally rotationally symmetric Bianchi-type Ⅱ string cosmological models with bulk viscosity areobtained, where an equation of state, p = kλ, and a relation between metric potentials, R = ASn, are adopted. Thephysical features of the models are also discussed. In special cases the model reduces to the string models withoutviscosity that was previously given in the literatures.

Higher dimensional bianchi type-V universe in creation-field cosmology

We have studied the Hoyle-Narlikar C-field cosmology with Bianchi type-V non static space- time in higher dimensions. Using methods of Narlikar and Padmanabham [1], the solutions have been studied when the creation field C is a function of time t only as space time is non static. The geometrical and physical aspects for model are also studied.

广义相对论中带体积粘滞性的毕安基-Ⅸ型宇宙弦模型(英文)

对定域旋转对称的毕安基-Ⅸ型宇宙弦模型进行了研究,讨论了两个模型,第一个模型中引入了一个普遍采用的状态方程ρ=kλ,第二个模型中引入了粘滞系数与体积膨胀系数成正比的条件ξ=hθ.我们对两个模型的物理和几何性质作了讨论,这些模型描述的是一个以大爆炸为开始的连续膨胀的宇宙模型,并把文献中的一些结果作为特例包括在内.