In this paper, a spatially homogeneous and anisotropic Bianchi type V model filled with an imperfect fluid with bulk viscosity and particle creation, is investigated within the framework of General Relativity. Particle creation and bulk viscosity have been considered as separate irreversible processes. The energy- momentum tensor is modified to accommodate the viscous pressure and creation pressure which is associated with creation of matter out of gravitational field. Exact solutions of the field equations are obtained by applying a special law of variation of Hubble parameter. Using this assumption, we obtain two types of cosmological models. We find a singularity in the first model whereas second model is non-singular. Further we separately study the bulk viscosity and particle creation in each model considering four different cases. The bulk viscosity coefficient $ζ$ is obtained for Truncated, Full Causal and Eckart theories in all cases. All physical parameters are calculated and thoroughly discussed in both models.
The Momentum 4-Vector in Bulk Viscous Bianchi Type-V Space-time
这篇论文已经被arXiv管理员删除，因为它抄袭了gr-qc/0611031，“Generation of Bianchi type V bulk粘性宇宙学模型与时间相关的Lambda-term，”由A. Pradhan，K. Jotania和A. Rai; Phys. Rev. D 41，1086（1990），“与Kerr-Newman黑洞相关的能量”，K. S. Virbhadra;和gr-qc/0303034，“宇宙在远程平行引力中的能量”，T.瓦格斯
In this paper we study the exact solutions for a viscous fluid distribution in Bianchi II, VIII, and IX models. The metric is simplified by assuming a relationship between the coefficients and the metric tensor. Solutions are obtained in two special cases: in one, an additional assumption is made where the matter density and the expansion scalar have a definite relation and in the other a barotropic equation of state between the matter density and the thermodynamic pressure is assumed. While the Bianchi II solutions are already found in the literature the other two classes of solutions are app…
A spatially homogeneous Bianchi type VI0 model containing a viscous fluid in the presence of an axial magnetic field has been studied. A barotropic equation of state together with a pair of linear relations among the square root of matter density, shear scalar, and expansion scalar have been assumed. Solutions are obtained in the presence of a magnetic field, only in two special cases, which are comparatively simpler. The complete solutions for this model in the absence of a magnetic field are also obtained. The presence of a magnetic field in the former case however, does not in effect cause …
The irrotational Bianchi V cosmological model under the influence of both shear and bulk viscosity, together with heat flux, has been studied. Exact solutions for the model are obtained with three physically viable assumptions. The first two relate the matter density, shear scalar, and expansion scalar and the third is a barotropic equation of state, connecting the matter density and thermodynamic pressure. The properties of the solutions are studied and the temperature distribution is also presented explicitly. It has been observed that along with the viscosity, heat flux further adds to the …
Within the quantum field theory approach and using the technique of Bogoliubov transformations, the von Neumann boson-antiboson pair creation quantum entanglement entropy is studied in the context of the noncommutative Bianchi I universe. It is shown that the latter have a behavior depending strongly on the choice of the noncommutativity θ parameter, k_{\perp}-frequency modes and the structure of the curved spacetime. Moreover, the relationship between the Bose-Einstein condensation and quantum entanglement is also discussed.
In this work we consider particle creation by the expansion of the universe, using two Bianchi type I anisotropic models. The particles studied are of spin 0 and 1/2. The cosmological models have rotational symmetry, which allows us to solve exactly the equations of motion. The number density of the created particles is calculated with the method of Bogolubov transformations.
Bianchi I cosmological models consisting of a fluid with both bulk and shear viscosity are studied. It is shown how the dynamical importance of the shear and the fluid density change in the course of evolution. Exact solutions with an equation of state $ρ= p$ for a stiff fluid are also obtained in several special cases, assuming the viscosity coefficients to be the power functions of the density. The results are, in some relevant cases, compared with those of Belinskii and Khalatnikov (1976) in the asymptotic limits and are seen to agree with them in that the models start with $ρ= 0$ at the be…
The present study deals with spatially homogeneous and totally anisotropic Bianchi type V cosmological model in presence of bulk viscous fluid source with time dependent gravitational constant G and cosmological term Lambda. The coefficient of bulk viscosity zeta is considered to be a quadratic function of Hubble parameter H (i.e. zeta=zeta_0+zeta_1H+zeta_2H^2, where zeta_0, zeta_1 and zeta_2 are constants). Exact solution of Einstein's field equations are obtained by using a particular form of Hubble parameter H i.e. H(a)=m(a^-n +1), where m>0, n>1, a being a scale factor and H=(da/dt)/a whic…
A spatially homogeneous and locally rotationally symmetric Bianchi type-II cosmological model under the influence of both shear and bulk viscosity has been studied. Exact solutions are obtained with a barotropic equation of state between thermodynamics pressure and the energy density of the fluid, and considering the linear relationships amongst the energy density, the expansion scalar and the shear scalar. Special cases with vanishing bulk viscosity coefficients and with the perfect fluid in the absence of viscosity have also been studied. The formal appearance of the solutions is the same fo…
The paper presents some exact solutions of Bianchi types I, III and Kantowski-Sachs cosmological models consisting of a dissipative fluid along with an axial magnetic field. A barytropic equation of state between the thermodynamic pressure and the matter density, together with a pair of linear relations between the matter density, the shear scalar, and the expansion scalar have been assumed for simplicity. The solutions are basically of two different types, one for the Bianchi-I and the other for Bianchi-III and Kantowski-Sachs type. The presence of the magnetic field, however, does not change…
In this paper, we have investigated a bulk viscous anisotropic Universe and constrained its model parameters with recent $H(z)$ and Pantheon compilation data. Using cosmic chronometric technique, we estimate the present value of Hubble's constant as $H_{0} = 69.39 \pm 1.54~km~s^{-1}Mpc^{-1}$, $70.016 \pm 1.65~km~s^{-1}Mpc^{-1}$ and $69.36 \pm 1.42~km~s^{-1}Mpc^{-1}$ by bounding our derived model with recent $H(z)$ data, Pantheon and joint $H(z)$ and Pantheon data respectively. The present age of the Universe is specified as $t_0= 0.9796H_0^{-1}\sim 13.79$ Gyrs. The model favours a transitionin…
Locally-rotationally-symmetric Bianchi type-I viscous and non -viscous cosmological models are explored in general relativity (GR) and in f(R,T) gravity. Solutions are obtained by assuming that the expansion scalar is proportional to the shear scalar which yields a constant value for the deceleration parameter (q=2). Constraints are obtained by requiring the physical viability of the solutions. A comparison is made between the viscous and non-viscous models, and between the models in GR and in f(R,T) gravity. The metric potentials remain the same in GR and in f(R,T) gravity. Consequently, the …
The non-commutative Bianchi I curved space-time vierbeins and spin connections are derived. Moreover, the corresponding non-commutative Dirac equation as well as its solutions are presented. As an application within the quantum field theory approach using Bogoliubov transformations, the von Neumann fermion-antifermion pair creation quantum entanglement entropy is studied. It is shown that its behaviour is strongly dependent on the value of the non-commutativity $θ$ parameter, $k_\perp$-modes frequencies and the structure of the curved space-time. Various discussions of the obtained features ar…
