Spherical top-hat collapse of a viscous unified dark fluid |
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Authors: | Wei Li Lixin Xu |
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Institution: | 1. Department of Physics, Bohai University, Jinzhou, 121013, People’s Republic of China 2. Institute of Theoretical Physics, Dalian University of Technology, Dalian, 116024, People’s Republic of China
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Abstract: | In this paper, we test the spherical collapse of a viscous unified dark fluid (VUDF) which has constant adiabatic sound speed and show the nonlinear collapse for VUDF, baryons, and dark matter, which are important in forming the large-scale structure of our Universe. By varying the values of the model parameters $\alpha $ and $\zeta _{0}$ , we discuss their effects on the nonlinear collapse of the VUDF model, and we compare its result to the $\Lambda $ CDM model. The results of the analysis show that, within the spherical top-hat collapse framework, larger values of $\alpha $ and smaller values of $\zeta _{0}$ make the structure formation earlier and faster, and the other collapse curves are almost distinguished with the curve of $\Lambda $ CDM model if the bulk viscosity coefficient $\zeta _{0}$ is less than $10^{-3}$ . |
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