Two component baryonic-dark matter structure formation in top-hat model

In this work we extend simple top-hat model of structure formation to the two component system made of baryonic and dark matter. We use Harrison-Zeldovich spectrum as the initial condition for the structures and calculate their evolution up to the present time. While we do not take into account some complications during the structure formation, such as the merging of galaxies, however this formalism can give us a qualitative picture from the formation of structures. We show that in this model small scale structures evolve faster than the larger ones and it predicts a down-top scenario for the structure formation. The trend of power spectrum in this model is compatible with the observations and results in σ8∼0.8. This formalism provides an analytic treatment of structure growth and can easily show the effect of the cosmological parameters on the formation of the structures. As an example, the effect of a parameterized dark energy model on the growth of the structures is investigated.