Eur. Phys. J. C (2014) 74: 2870
https://doi.org/10.1140/epjc/s10052-014-2870-y

Regular Article - Theoretical Physics

Spherical top-hat collapse of a viscous unified dark fluid

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

^* e-mail: liweizhd@126.com

Received: 7 January 2014
Accepted: 24 April 2014
Published online: 7 May 2014

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 and , we discuss their effects on the nonlinear collapse of the VUDF model, and we compare its result to the CDM model. The results of the analysis show that, within the spherical top-hat collapse framework, larger values of and smaller values of make the structure formation earlier and faster, and the other collapse curves are almost distinguished with the curve of CDM model if the bulk viscosity coefficient is less than .