Bianchi Type V String Cosmological Models in General Relativity

Bianchi type V string cosmological models in general relativity are investigated. To get the exact solution of Einstein's field equations, we have taken some scale transformations followed by Camci $\it et ~ al$ (2001). It is shown that Einstein's field equations are solvable for any arbitrary cosmic scale function. Solution for particular form of cosmic scale functions are also obtained. Some physical and geometrical aspects of the models are discussed.Comment: 12 pages, Accepted version in Pramana - J. Physic

Some LRS Bianchi-I String Cosmological Models with Variable Deceleration Parameter

The present study deals with LRS Bianchi type I cosmological model representing massive string. The energy-momentum tensor for such string as formulated by Letelier (1983) is used to construct massive string cosmological models for which we assume that the shear scalar ($\sigma$) is proportional to the expansion scalar ($\theta$). The study reveals that massive strings dominate the early Universe. The strings eventually disappear from the Universe for sufficiently large time, which is in agreement with the current astronomical observations. Some physical and geometrical behaviour of models are also discussed.Comment: 11 pages, 6 figures, Unlike the previous version the new one contains the variable D

Anisotropic massive strings in scalar-tensor theory of gravitation

We present the model of anisotropic universe with string fluid as source of matter within the framework of scalar-tensor theory of gravitation. Exact solution of field equations are obtained by applying Berman's law of variation of Hubble's parameter which yields a constant value of DP. The nature of classical potential is examined for the model under consideration. It has been also found that the massive strings dominate in early universe and at long last disappear from universe. This is in agreement with current astronomical observations. The physical and dynamical properties of model are also discussed.Comment: 12 pages, 5 figur

Lyra's cosmology of inhomogeneous universe with electromagnetic field

The plane-symmetric inhomogeneous cosmological models of perfect fluid distribution with electro-magnetic field is obtained in the framework of Lyra's geometry. To get the deterministic solution, I have considered $A=f(x)\nu(t)$, $B=g(x)\mu(t)$ and $C=h(x)\mu(t)$, where A, B and C are metric coefficients. It has been found that the solutions generalize the solution obtained by Pradhan, Yadav and Singh (2007) and are consistent with the recent observations of type Ia supernovae. A detailed study of physical and kinematical properties of the models have been carried out.Comment: 25 pages, 2 figure

Generation of Bianchi Type V String Cosmological Models with Bulk Viscosity

Bianchi type V string cosmological models with bulk viscosity for massive string are investigated. The bulk viscosity is assumed to vary with time in such a manner that it is related to simple power function of the energy density. Using generation technique (Camci~et~al., 2001), it is shown that Einstein's field equations are solvable for any arbitrary cosmic scale function. Solution for particular form of cosmic scale functions are also obtained. It is found that solutions based on generation technique are relevant to the observational results. Some physical and geometrical aspect of the models are also discussed.Comment: 12 pages, 3 figures, Typose removed, To appear in Rom. Rep. Physic

Bianchi-V string cosmology with power law expansion in f(R,T)f(R, T) Gravity

In this paper, we search the existence of Bianchi-V string cosmological model in $f(R,T)$ gravity with power law expansion. Einstein's field equations have been solved by taking into account the law of variation of Hubble's parameter that yields the constant value of deceleration parameter (DP). We observe that the massive strings dominate the early universe but they do not survive for long time and finally disappear from the universe. We examine the nature of classical potential and also discuss the physical properties of universe.Comment: 6 pages, 4 figure

A transitioning universe with anisotropic dark energy

In this paper, we present a model of transitioning universe with minimal interaction between perfect fluid and anisotropic dark energy in Bianchi I space-time. The two sources are assumed to minimally interacted and therefore their energy momentum tensors are conserved separately. The explicit expression for average scale factor are considered in hybrid form that gives time varying deceleration parameter which describes both the early and late time physical features of universe. We also discuss the physical and geometrical properties of the model derived in this paper. The solution is interesting physically as it explain accelerating universe as well as singularity free universe.Comment: 7 pages, 2 figure panel

LRS Bianchi-I Anisotropic Cosmological Model with Dominance of Dark Energy

The present study deals with spatially homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi type I cosmological model with dominance of dark energy. To get the deterministic model of Universe, we assume that the shear scalar $(\sigma)$ in the model is proportional to expansion scalar $(\theta)$. This condition leads to $A=B^{n}$, where $A$,\;$B$ are metric potential and $n$ is positive constant. It has been found that the anisotropic distribution of dark energy leads to the present accelerated expansion of Universe. The physical behavior of the Universe has been discussed in detail.Comment: 11 pages, 4 figures, Accepted for publication in Astrophysics and Space Scienc

Invariant Bianchi type I models in f(R,T)f\left(R,T\right) Gravity

In this paper, we search the existence of invariant solutions of Bianchi type I space-time in the context of $f\left(R,T\right)$ gravity. The exact solution of the Einstein's field equations are derived by using Lie point symmetry analysis method that yield two models of invariant universe for symmetries $X^{(1)}$ and $X^{(3)}$. The model with symmetries $X^{(1)}$ begins with big bang singularity while the model with symmetries $X^{(3)}$ does not favour the big bang singularity. Under this specification, we find out at set of singular and non singular solution of Bianchi type I model which present several other physically valid features within the framework of $f\left(R,T\right)$.Comment: 14 Pages, 2 Figure panels, Textual changes and 01 reference adde

Symmetry Group Analysis for perfect fluid Inhomogeneous Cosmological Models in General Relativity

In this paper, we have searched the existence of the similarity solution for plane symmetric inhomogeneous cosmological models in general relativity. The matter source consists of perfect fluid with proportionality relation between expansion scalar and shear scalar. The isovector fields of Einstein's field equation for the models under consideration are derived. A new class of exact solutions of Einstein's field equation have been obtained for inhomogeneous space-time. The physical behaviors and geometric aspects of the derived models have been discussed in detail.Comment: 13 page