Solving the main cosmological puzzles with a generalized time varying vacuum energy

Abstract

We study the dynamics of the FLRW flat cosmological models in which the vacuum energy density varies with time, $\Lambda (t)$. In particular, we investigate the dynamical properties of a generalized vacuum model and we find that under certain conditions the vacuum term in the radiation era varies as $\Lambda (z)\propto (1+z{)}^4$, while in the matter era we have $\Lambda (z)\propto (1+z{)}^3$ up to $z\simeq 3$ and $\Lambda (z)=\Lambda$ for $z\le 3$. The confirmation of such a behavior would be of paramount importance because it could provide a solution to the cosmic coincidence problem as well as to the fine tuning problem, without changing the well known (from the concordance $\Lambda$ cosmology) Hubble expansion.

9 pages, 2 figures, Accepted for publication by Astronomy and Astrophysics

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• Constraints on Cold Dark Matter Accelerating Cosmologies and Cluster Formation
• Dynamics and cosmological evolution in Λ-varying cosmology
• Nonsingular Decaying Vacuum Cosmology and Entropy Production
• The spherical collapse model in time varying vacuum cosmologies
• Thermodynamical aspects of running vacuum models
• Testing dynamical vacuum models with CMB power spectrum from Planck
• Dynamics in Varying vacuum Finsler-Randers Cosmology
• Cosmological singularities and analytical solutions in varying vacuum cosmologies
• LRS Bianchi I model with constant expansion rate in $f(R,T)$ gravity
• Black Hole Formation with an Interacting Vacuum Energy Density
• Analytic solutions in Einstein-aether scalar field cosmology
• Phenomenological Dark Energy model with hybrid dynamic Cosmological Constant
• Einstein-aether models III: conformally static metrics, perfect fluid and scalar fields
• The cosmic censorship conjecture in a higher dimensional spacetime with an interacting vacuum energy
• Cosmological solutions with time-delay