arXiv subjects

Raj Bali

Publications and source records attributed to Raj Bali.

5 recordsLinked to original sources

arXiv2014

String Cosmological Model in Cylindrically Symmetric Inhomogeneous Universe with Electromagnetic Field

Cylindrically symmetric inhomogeneous string cosmological models in presence of electromagnetic field is investigated. We have assumed that $F_{12}$ is the only non-vanishing component of $F_{ij}$. The Maxwell's equations require that $F_{12}$ is the function of $x$ and $t$ both and the magnetic permeability is the function of $x$ and $t$ both. To get the deterministic solution, it has been assumed that the expansion ($θ$) in the model is proportional to the eigen value $σ^{1}_{1}$ of the shear tensor $σ^{i}_{j}$. The derived model represents the inflationary scenario as the proper volume increases exponentially with cosmic time. It is observed that the model has a point type singularity. The physical and geometric aspects of the model are also discussed.

gr-qc↗

arXiv2012

Bianchi Type V Viscous Fluid Cosmological Models in Presence of Decaying Vacuum Energy

Bianchi type V viscous fluid cosmological model for barotropic fluid distribution with varying cosmological term $Λ$ is investigated. We have examined a cosmological scenario proposing a variation law for Hubble parameter $H$ in the background of homogeneous, anisotropic Bianchi type V space-time. The model isotropizes asymptotically and the presence of shear viscosity accelerates the isotropization. The model describes a unified expansion history of the universe indicating initial decelerating expansion and late time accelerating phase. Cosmological consequences of the model are also discussed.

gr-qc↗

arXiv2008

Magnetized Bianchi Type $VI_{0}$ Barotropic Massive String Universe with Decaying Vacuum Energy Density $Λ$

Bianchi type $VI_{0}$ massive string cosmological models using the technique given by Letelier (1983) with magnetic field are investigated. To get the deterministic models, we assume that the expansion ($θ$) in the model is proportional to the shear ($σ$) and also the fluid obeys the barotropic equation of state. It was found that vacuum energy density $Λ\propto \frac{1}{t^{2}}$ which matches with natural units. The behaviour of the models from physical and geometrical aspects in presence and absence of magnetic field is also discussed.

gr-qc↗

arXiv2007

Bianchi Type I Massive String Magnetized Barotropic Perfect Fluid Cosmological Model in General Relativity

Bianchi type I massive string cosmological model with magnetic field of barotropic perfect fluid distribution through the techniques used by Latelier and Stachel, is investigated. To get the deterministic model of the universe, it is assumed that the universe is filled with barotropic perfect fluid distribution. The magnetic field is due to electric current produced along x-axis with infinite electrical conductivity. The behaviour of the model in presence and absence of magnetic field together with other physical aspects is further discussed.

gr-qc↗

arXiv2007

Bianchi Type III String Cosmological Models with Time Dependent Bulk Viscosity

Bianchi type III string cosmological models with bulk viscous fluid for massive string are investigated. To get the determinate model of the universe, we have assumed that the coefficient of bulk viscosity ($ξ$) is inversely proportional to the expansion ($θ$) in the model and expansion ($θ$) in the model is proportional to the shear ($σ$). This leads to $B = \ell C^{n}$, $\ell$ and $n$ are constants. The behaviour of the model in presence and absence of bulk viscosity, is discussed. The physical implications of the models are also discussed in detail.

gr-qc↗