The spherical collapse model in time varying vacuum cosmologies

Understand

We investigate the virialization of cosmic structures in the framework of flat FLRW cosmological models, in which the vacuum energy density evolves with time.

• In particular, our analysis focuses on the study of spherical matter perturbations, as they decouple from the background expansion, "turn around" and finally collapse.
• We generalize the spherical collapse model in the case when the vacuum energy is a running function of the Hubble rate, $\Lambda=\Lambda(H)$.
• A particularly well motivated model of this type is the so-called quantum field vacuum, in which $\Lambda(H)$ is a quadratic function, $\Lambda(H)=n_0+n_2\,H^2$, with $n_0\neq 0$.