Nonlinear dark matter collapse under diffusion

Diffusion is one of the physical processes allowed for describing the large scale dark matter dynamics. At the same time, it can be seen as a possible mechanism behind the interacting cosmologies. We study the nonlinear spherical “top-hat” collapse of dark matter which undergoes velocity diffusion into a solvent dark energy field. We show constraints on the maximum magnitude allowed for the dark matter diffusion. Our results reinforce previous analysis concerning the linear perturbation theory.

Figure 1

Dark matter perturbation growth as a function of the redshift.

Figure 2

Perturbation growth of baryons as a function of the redshift.

Figure 3

Evolution of the expansion rate of the collapsed region.

Figure 4

Dark matter perturbation growth as a function of the redshift.

Figure 5

Perturbation growth of the quantity ${\mathrm{\Delta }}_T$ as a function of the redshift.

Figure 6

Perturbation growth of baryons as a function of the redshift.

Figure 7

Evolution of the expansion rate of the collapsed region.