The bulk viscous string cosmology in an anisotropic universe with late time acceleration

作     者：Hassan Amirhashchi 

作者机构：Department of PhysicsMahshahr BranchIslamic Azad University 

出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)

年 卷 期：2013年第13卷第4期

页      面：387-398页

核心收录：

学科分类：07[理学] 070401[理学-天体物理] 0704[理学-天文学] 

基　　金：supported by a research fund from the Mahshahr Branch of Islamic Azad University under the project entitled "Study of the homogenous and anisotropic cosmological models by considering the gravitational effects of viscosity and cosmic strings" 

主　　题：cosmology: theory    viscous fluid    massive string 

摘      要：A model of a cloud formed by massive strings is used as a source of Bianchi type II cases. We assume that the expansion （θ） in the model is proportional to the shear （σ）. To get an exact solution, we consider the equation of state of the fluid to be in the stiff form. It is found that the bulk viscosity played a very important role in the history of the universe. In the presence of bulk viscosity the particles dominate over strings whereas in the absence of it, strings dominate over the particles, which is not consistent with recent observations. Also we observe that the viscosity causes the expansion of the universe to be accelerating. Our models are evolving from an early decelerating phase to a late time accelerating phase. The physical and geometrical behaviors of these models are discussed.