Spherical Collapse for Viscous Generalized Chaplygin Gas Model
  The nonlinear collapse for viscous generalized Chaplygin gas Model (VGCG) was
analyzed in the framework of spherical top-hat collapse. As the VGCG and
baryons are essential to form the large scale structure, we focused on their
nonlinear collapse in this paper. We discussed the influence of model
parameters $\alpha$ and $\zeta_{0}$ on the spherical collapse by varying their
values and compare with $\Lambda CDM$. The results show that, for the VGCG
model, smaller $\zeta_{0}$ and larger $\alpha$ make the structure formation
earlier and faster, and the collapse curves of VGCG model is almost
distinguished with the $\Lambda CDM$ model when the model parameter $\alpha$ is
less than $10^{-2}$.
