Bianchi Type IX Magnetized Bulk Viscous String Cosmological Model in General Relativity

Abstract

Abstract. In this paper we present a bulk viscous magnetized Bianchi type IX string cosmological model in general relativity. In order to find determinate solution of the investigated model, we assume the conditions :(i) Scalar expansion is proportional to shear scalar and (ii) ξθ = constant, where ξ is bulk viscosity and θ is scalar expansion. Some physical and geometrical properties of the investigated model are also discussed. Keywords:Bianchi type IX space time, bulk viscous, magnetized cosmic string. IntroductionIt is well known that Einstein's general theory of relativity has been successful in finding different models for the universe. Einstein's theory of general relativity is considered as the only successful theory of gravitation in terms of geometry which has the most beautiful structure of the theoretical physics. In recent years, Bianchi type-IX cosmological models are very popular for relativistic studies. These models are also used to examine the role of certain anisotropic sources during the formation of large scale structure as we see the universe today. Many researchers have taken keen interest in studying Bianchi Type IX universes, because familiar solutions like Robertson Walker universe with positive curvature, the de-Sitter universe, the Taub On the other hand, Bulk viscosity plays a significant role in the early evolution of the universe and contributes to the accelerated expansion phase of the universe popularly known as the inflationary phase. The effect of viscosity on the evolution of cosmological models and the role of viscosity in avoiding the initial big bang singularity have been studied by several authors [5][6]. In late nineties, two teams studying distant type Ia-supernovae (SNe-Ia) independently presented evidence of expansion [7][8] and confirmed later by cross checks from the cosmic microwave background radiation (CMBR) [9] and large scale structure (LSS) [10][11][12][13].In addition, the magnetic field has important role at the cosmological scale and is present in galactic and intergalactic space. It plays a vital role in the description of the energy distribution in the universe as it contains highly ionized matter. Strong magnetic fields can be created due to adiabatic compression in cluster of galaxies. Large scale magnetic fields give rise to anisotropies in the universe. Primordial magnetic fields of cosmological origin have been discussed by Asseo et.al [14] and Madsen [15]. Melvin [16] suggested, in the cosmological solution for dust and electromagnetic fields, that during the evolution of the universe, the matter was in highly ionized state and smoothly coupled with electromagnetic and consequently formed a neutral matter as a result of expansion of the universe. Hence, in a string dust universe the presence of magnetic fields is not unrealistic. The magnetic field has the significant role in the dynamics of the universe depending on the direction of the field lines [17][18]

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