From de Sitter to de Sitter: Decaying Vacuum Models as a Possible Solution to the Main Cosmological Problems

Figure 1

Standard coincidence problem in the cosmic concordance model (CDM). Solid and dashed lines represent the evolution of the vacuum () and total matter-radiation () density parameters. The circle marks the low (and unique!) redshift presenting the extreme coincidence between the density parameter of the vacuum and material medium. Note that the model discussed here is fully equivalent to CDM when the time dependent corrections in the decay expression are neglected [see (5)].