Cosmic expansion and structure formation in running vacuum cosmologies

Abstract

We investigate the dynamics of the FLRW flat cosmological models in which the vacuum energy varies with redshift. A particularly well motivated model of this type is the so-called quantum field vacuum, in which both kind of terms $H^2$ and constant appear in the effective dark energy density affecting the evolution of the main cosmological functions at the background and perturbation levels. Specifically, it turns out that the functional form of the quantum vacuum endows the vacuum energy of a mild dynamical evolution which could be observed nowadays and appears as dynamical dark energy. Interestingly, the low-energy behaviour is very close to the usual $\Lambda$CDM model, but it is by no means identical. Finally, within the framework of the quantum field vacuum we generalize the large scale structure properties, namely growth of matter perturbations, cluster number counts and spherical collapse model.

Comments: 16 pages, 2 figures Invited paper for the Special Issue: "Fundamental Constants in Physics and Their Time Variation" (Modern Physics Letters A, Guest Editor Joan Solà)