Running Vacuum in the Universe: current phenomenological status

TL;DR

This paper reviews dynamical vacuum models where vacuum energy density evolves with the Hubble rate, providing a phenomenological framework that fits cosmological data well and challenges the standard cosmological constant model.

Contribution

It presents a comprehensive review of running vacuum models, highlighting their ability to unify inflation, radiation, matter, and dark energy epochs within a single framework.

Findings

Running vacuum models fit cosmological data better than ΛCDM.

These models can incorporate inflation and late-time acceleration.

Observations favor a dynamic vacuum over a static cosmological constant.

Abstract

I review the excellent phenomenological status of a class of dynamical vacuum models in which the vacuum energy density, $\rho_{\Lambda}=\rho_{\Lambda}(H)$, as a function of the Hubble rate, evolves through its interaction with dark matter and/or through the accompanying running of the gravitational coupling $G$, including the possibility of being self-conserved with a nontrivial effective equation of state. Some of these models have been used to incorporate into a single vacuum structure the rapid stage of inflation, followed by the standard radiation and cold dark matter epochs all the way down until the dark energy era. Remarkably, the running vacuum models (RVM's) render an outstanding phenomenological description of the main cosmological data at a level that is currently challenging the concordance $\Lambda$CDM model, thereby implying that present observations seem to point to a running vacuum rather than to a rigid cosmological constant $\Lambda$ in our Universe.