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 forVUDF, baryons, and dark matter, which are important in forming the large-scale structure of our Universe. By varying the values of the model parameters α and ζ0, we discuss their effects on the nonlinear collapse of the VUDF model, and ...

If a magnetic field is frozen into a plasma that undergoes spherical compression then the magnetic field B varies with the plasma density ρ according to B ∝ ρ. In the gravitational collapse of cosmological density perturbations, however, quasi-spherical evolution is very unlikely. In anisotropic collapses the magnetic field can be a much steeper function of gas density than in the isotropic cas...