Bulg. J. Phys. vol.39 no.3 (2012), pp. 248-269

Anisotropic Bianchi Type-III String Cosmological Models in Normal Gauge for Lyra's Manifold with Electromagnetic Field

A. Pradhan1, R. Zia2, H. Amirhashchi3
1Department of Mathematics, Hindu Post-graduate College, Zamania-232 331, Ghazipur, India
2Department of Mathematics, T.D. Post-graduate College, Jaunpur-232 331, U.P., India
3Department of Physics, Mahshahr Branch, Islamic Azad University, Mahshahr, Iran
Abstract. The present study deals with a spatially homogeneous and anisotropic Bianchi type-III cosmological models representing massive strings in normal gauge for Lyra's manifold with electromagnetic field. The energy-momentum tensor for such string as formulated by Letelier (1983) is used to construct massive string cosmological models for which we assume that the expansion (θ) in the model is proportional to the eigenvalue σ2 2 of the shear tensor σj i. This condition leads to B = l1(AC)m1, where A, B and C are the metric coefficients and l1, m1 are arbitrary constants. Our models are in accelerating phase which is consistent to the recent observations. It has been found that the displacement vector β behaves like cosmological term Λ in the normal gauge treatment and the solutions are consistent with recent observations of SNe Ia supernovae. It is also observed that in early stage of the evolution of the universe string dominates over the particle whereas the universe is dominated by massive string at the late time. Some physical and geometric behaviour of the models have also been discussed in presence and absence of magnetic field.

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