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 = ℓC n , where ℓ 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.

Bianchi Type I magnetized string cosmological model following the techniques used by Letelier and Stachel, is investigated. To get a determinate model, we assume a condition ∈ =λ (geometric string) where ∈ is the rest energy density, λ the string tension density and expansion (θ) is proportional to eigen value σ 1 1 of shear tensor (σ i j ), which leads to A = (BC) n where A, B, C are metric potentials and and n are constants. The behaviour of the model in presence and absence of magnetic field is discussed. The physical and geometrical aspects of the model are also discussed.

We have investigated Bianchi type IX string cosmological models in general relativity. To get a determinate solution, we have assumed a condition i.e. rest energy density for a cloud of strings is equal to the string tension density. The various physical and geometrical aspects of the models are also discussed.

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