Bianchi Type-III String Cosmological Model with Bulk Viscosity in General Relativity

The Bianchi type-III cosmological model for a cloud string with bulk viscosity are studied. To obtain a determinate solution, it is assumed that the coefficient of bulk viscosity is a power function of the
scalar of expansion zeta = kθ^m and the shear scalar is proportional to scalar of expansion σ ∝ θ, which leads to the relation between metric potentials B = Cⁿ. The physical features of the model are also discussed. It is found that the power index m has significant influence on the string model. There is a ``big bang'' start in the model when m≤1 but there is no the big-bang start when m > 1. In the special case m = 0, the model reduces to the string model of constant coefficient of bulk viscosity that was the result previously given in the literature.