Bianchi type-V Lyttleton-Bondi universe

The exterior field of the Bianchi type-V metric in the Lyttleton-Bondi universe is considered. It is shown that the Bianchi type-V Lyttleton-Bondi universe, under certain conditions, does not exist.     

Bianchi type-V cosmological models with perfect fluid and dark energy

We consider a self-consistent system of Bianchi type-V cosmology and binary mixture of perfect fluid and dark energy. The perfect fluid is taken to be one obeying the usual equation of state p=γ ρ with γ∈[0,1]. The dark energy is considered to be either the quintessence or Chaplygin gas. Exact solutions to the corresponding Einstein equations are obtained as a quadrature. The cases of disordered radiation and models with power-law and exponential expansion have discussed in detail. For large t, the models tend to be isotropic.     

Interacting holographic dark energy with variable deceleration parameter and accreting black holes in Bianchi type-V universe

Dust-ion-acoustic (DIA) waves in an unmagnetized dusty plasma system consisting of inertial ions, negatively charged immobile dust, and superthermal (kappa distributed) electrons with two distinct temperatures are investigated both numerically and analytically by deriving Korteweg–de Vries (K-dV), modified K-dV (mK-dV), and Gardner equations along with its double layers (DLs) solutions using the reductive perturbation technique. The basic features of the DIA Gardner solitons (GSs) as well as DLs are studied, and an analytical comparison among K-dV, mK-dV, and GSs are also observed. The parametric regimes for the existence of both the positive as well as negative SWs and negative DLs are obtained. It is observed that superthermal electrons with two distinct temperatures significantly affect on the basic properties of the DIA solitary waves and DLs; and depending on the parameter μ _c (the critical value of relative electron number density μ _e1), the DIA K-dV and Gardner solitons exhibit both compressive and rarefactive structures, whereas the mK-dV solitons support only compressive structures and DLs support only the rarefactive structures. The present investigation can be very effective for understanding and studying various astrophysical plasma environments (viz. Saturn magnetosphere, pulsar magnetosphere, etc.).     

Holographic dark energy with linearly varying deceleration parameter and escaping big rip singularity of the Bianchi type-V universe

The present work deals with the accretion of two minimally interacting fluids: dark matter and a hypothetical isotropic fluid as the holographic dark energy components onto black hole and wormhole in a spatially homogeneous and anisotropic Bianchi type-V universe. To obtain an exact solution of the Einstein’s field equations, we use the assumption of linearly varying deceleration parameter. Solution describes effectively the actual acceleration and indicates a big rip type future singularity of the universe. We have studied the evolution of the mass of black hole and the wormhole embedded in this anisotropic universe in order to reproduce a stable universe protected against future-time singularity. It is observed that the accretion of these dark components leads to a gradual decrease and increase of black hole and wormhole mass respectively. Finally, we have found that contrary to our previous case (Sarkar in Astrophys. Space. Sci. 341:651, 2014a), the big rip singularity of the universe with a divergent Hubble parameter of this dark energy model may be avoided by a big trip.     

Bianchi type-III universe with perfect fluid

We study Bianchi type-III cosmological model filled with perfect fluid in the presence of cosmological constant Λ(t). The Hubble law utilised yields a constant value of deceleration parameter. Physical and Kinematical properties of the model have also studied.      

Some anisotropic dark energy models in Bianchi type-V space-time

The paper deals with Bianchi type V Universe, which has dynamical energy density. We consider Bianchi type V space-time, introducing three different skewness parameters along spatial directions to quantify the deviation of pressure from isotropy. To study the anisotropic nature of the dynamical dark energy, we assume that the skewness parameters are time dependent. It is found that the Universe achieves flatness in quintessence model. The physical behavior of the Universe has been discussed in detail.     

Statefinder diagnostic for variable modified Chaplygin gas in Bianchi type-V universe

The Bianchi type-V cosmological model with variable modified Chaplygin gas having the equation of state p=Aρ−B/ρ ^α , where 0≤α≤1, A is a positive constant and B is a positive function of the average scale factor a(t) of the universe [i.e. B=B(a)] has been studied. While studying its role in accelerated phase of the universe, it is observed that the equation of state of the variable modified Chaplygin gas interpolates from radiation dominated era to quintessence dominated era. The statefinder diagnostic pair {r,s} is adopted to characterize different phases of the universe.     

A tilted Bianchi type-V perfect fluid solution for stiff matter

We present a solution to the Einstein field equations for a massless scalar field in a Bianchi type-V spacetime, which can be interpreted as a solution for a perfect fluid with the equation of state of stiff matter. This solution complements a solution previously given by us for an anisotropic fluid.     

Bianchi type VI1 cosmological model with wet dark fluid in scale invariant theory of gravitation

In this paper, we have investigated Bianchi type VI _h , II and III cosmological model with wet dark fluid in scale invariant theory of gravity, where the matter field is in the form of perfect fluid and with a time dependent gauge function (Dirac gauge). A non-singular model for the universe filled with disorder radiation is constructed and some physical behaviors of the model are studied for the feasible VI _h (h=1) space-time.     

Bianchi type-V anisotropic cosmological models in certain theories of gravitation with perfect fluid distribution

Exact Bianchi type-V cosmological models are presented in Einstein’s theory of gravitation with cosmological constant Λ in case of perfect fluid distribution. Also obtained Bianchi type-V cosmological models in a scalar-tensor theory of gravitation proposed by Saez and Ballester (1986) in case of perfect fluid distribution using and without using negative constant deceleration parameter. Some physical and geometrical properties of the models are also discussed.     

Bianchi type-V cosmological model with purely magnetic solution

In the present paper we study some new aspects of the Bianchi type-V space time. The Electric and Magnetic parts of Weyl tensors are calculated in terms of tilted congruence and discussed the purely magnetic Weyl tensor. Einstein field equations for purely magnetic space time are obtained and solution of such field equations called purely magnetic solution. To get deterministic solutions of the field equations we consider a new law of variation of average scale factor which yields time dependent deceleration parameter. Certain physical and geometrical properties of the model are also discussed.     

Homogeneous space time with wet dark fluid

In this paper, we have constructed Wet Dark Fluid (WDF) model in an anisotropic homogeneous space-time namely Marder’s space time. We discussed two type of models as: power law expansion model and exponential expansion model. Also some physical parameters of the model are obtained and discussed.     

An interacting scenario for dark energy in a Bianchi type-I universe

We study the interaction between dark energy(DE) and dark matter in the scope of anisotropic Bianchi type-I space-time. First we derive the general form of the DE equation of state(EoS) parameter in both non-interacting and interacting cases and then we examine its future by applying a hyperbolic scale factor. It is shown that in the non-interacting case, depending on the value of the anisotropy parameter K,the DE EoS parameter varies from phantom to quintessence whereas in the interacting case the EoS parameter varies in the quintessence region. However, in both cases, the DE EoS parameter ωdeultimately(i.e. at z =-1) tends to the cosmological constant(ωde=-1). Moreover, we fix the cosmological bound on the anisotropy parameter K by using recent observational data about the Hubble parameter.     

String cosmology with magnetized bulk viscous fluid in Bianchi I universe

The objective of the present paper is to study an anisotropic Bianchi-I cosmological model filled with bulk viscous fluid and magnetic field in string cosmology. The magnetic field is due to an electric current produced along the x-axis. The expansion in the model is considered to be proportional to one of the components of the shear tensor. We obtain two different quadrature forms of volume scale factor by considering two different relations between bulk viscosity and expansion scalar. We discuss the behavior of the classical potential with respect to the volume scale factor in the presence or absence of magnetic field and bulk viscosity in each case. We observe the role of bulk viscosity on the classical potential and also on the choices of bulk viscous pressure. By introduction of magnetic field or bulk viscosity or both into the model it results in changes in the potential as well as in volume scale factors. The physical and geometrical aspects of the solutions are discussed in detail.     

Dynamics of a magnetized Bianchi VI 0 universe with anisotropic fluid

We discuss spatially homogeneous and anisotropic Bianchi type VI ₀ cosmological model with anisotropic fluid and magnetic field. The energy-momentum tensor consists of anisotropic fluid with anisotropic EoS and a uniform magnetic field of energy density ρ _B . Exact solution of the field equations is obtained by using the condition that expansion is proportional to the shear scalar. We focus on the future evolution of the model both in the presence and absence of magnetic field. In particular, we address the question whether these models approach to isotropy.     

LRS Bianchi type-V universes filled with matter and radiation

In this paper we have investigated some LRS Bianchi type-V cosmologicla models representing a viscous fluid distribution with a null electromagnetic field and streaming neutrinos. Various physical and kinematical features of these models have also been explored.     

Bianchi type-V radiating model in self-creation cosmology

The spatially-homogeneous and anisotropic cosmological model in self-creation theory of gravitation proposed by Barber, is obtained in the presence of perfect fluid with disordered radiation and the metric is of Bianchi type-V. Some physical properties of the model are discussed.     

Comment on the GRT-LRS Bianchi type-V solutions

We wish to point out that the locally rotationally symmetric (LRS) Bianchi type-V electromagnetic solutions recently given by Roy and Singh (1983) on the basis of the general theory of relativity (GRT) are wrong. The correct electromagnetic solutions are nothing but the vacuum and stiff matter solutions first given by Ftaclas (1978), which have been generalized by Jantzen (1980) and independently by Lorenz (1981).     

Bianchi type-I Lyttleton-Bondi universe

We present a scalar-tensor theory whose weak field limit gives exactly the potential proposed by Fischbachet al. (1986). The three experimental constantsG , , and are related to three parameters in our theory. At the level of the theory we have obtained the field produced by a source. The way this field should couple with a massive and charged particle (baryonic hypercharge) is a matter beyond the scope of this work.