Hints of dynamical vacuum energy in the expanding Universe

TL;DR

This paper investigates a class of cosmological models with a time-varying vacuum energy term, showing they fit observational data better than the standard Lambda-CDM model, suggesting evidence for dynamical dark energy.

Contribution

It introduces and tests a general dynamical vacuum model with a Hubble-dependent cosmological term, providing empirical support for evolving dark energy.

Findings

Dynamical vacuum models fit expansion and structure formation data better than Lambda-CDM.

Models with a Hubble-dependent vacuum energy are consistent with quantum field theory in curved spacetime.

Results support the possibility of a time-evolving cosmic vacuum energy.

Abstract

Recently there have been claims on model-independent evidence of dynamical dark energy. Herein we consider a fairly general class of cosmological models with a time-evolving cosmological term of the form $\Lambda(H)=C_0+C_H H^2+C_{\dot{H}} \dot{H}$, where $H$ is the Hubble rate. These models are well motivated from the theoretical point of view since they can be related to the general form of the effective action of quantum field theory in curved spacetime. Consistency with matter conservation can be achieved by letting the Newtonian coupling $G$ change very slowly with the expansion. We solve these dynamical vacuum models and fit them to the wealth of expansion history and linear structure formation data. The results of our analysis show a significantly better agreement as compared to the concordance $\Lambda$CDM model, thus supporting the possibility of a dynamical cosmic vacuum.