Viscous String Cosmological Models Research Articles

Viscous string cosmological models in alternative theory of gravity

In present communication, the Bianchi type-III, viscous string cosmological models have been investigated in scalar-tensor Brans-Dicke gravity. To obtain an exact solution of the Einstein field equations (EFE), it is assumed that the viscosity is the power function of energy density and the deceleration parameter (DP) as a function of cosmic time with suitable relation i.e. a(t)=[sinh(αt)]1/n , here α,n≠0 are constants. It is observed that the power index has the important significance on the evolution of string cosmological models. It is also noticed that the string tension density (λ) is increasing function of time where as the energy density (ρ) and the cosmological constant (Λ) are decreasing with time and converges to a small value at late time. For better understanding of the model, we have also presented the kinematic and geometric properties of the models.

Bulk Viscus Fluid Plane Symmetric String Dust Magnetised Cosmological Model in General Relativity

In this paper we have investigated bulk viscous fluid plane symmetric dust magnetized string cosmological model. To get a deterministic model, it is assumed that e=λ, and a relation between metric potential B=RAn. The behaviour of the model in the presence and absence of magnetic field together with physical and geometrical aspects of the model are also discussed.

LRS Bianchi Type V bulk viscous fluid string dust cosmological model in general relativity

An LRS Bianchi Type V bulk viscous fluid dust distribution string cosmological model in General Relativity is investigated. It has been shown that if coefficient of bulk viscosity (ζ) is proportional to the expansion (θ) in the model then string cosmological model for Bianchi Type V space-time is possible. In absence of bulk viscosity(ζ) i.e. when ζ → 0 then there is no string cosmological model for Bianchi Type V space-time. The physical and geometrical aspects are also discussed.