Viscous string cosmological models in alternative theory of gravity

Abstract

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.