A number of challenges to the standard Λ CDM model have been emerging during the past
few years as the accuracy of cosmological observations improves. In this review we discuss …

Abstract Recent Baryon Acoustic Oscillation (BAO) measurements released by DESI, when
combined with Cosmic Microwave Background (CMB) data from Planck and two different …

The renormalization of the vacuum energy in quantum field theory (QFT) is usually plagued
with theoretical conundrums related not only with the renormalization procedure itself, but …

The cosmological constant (CC) term in Einstein's equations, Λ, was first associated to the
idea of vacuum energy density. Notwithstanding, it is well-known that there is a huge, in fact …

I review the problem of dark energy focussing on cosmological constant as the candidate
and discuss what it tells us regarding the nature of gravity. Section 1 briefly overviews the …

Recent studies of quantum field theory in FLRW spacetime suggest that the cause of the
speeding up of the universe is the running vacuum (RV), see Moreno-Pulido and Solà …

Despite the many outstanding cosmological observations leading to a strong evidence for a
non-vanishing cosmological constant (CC) term Λ in the gravitational field equations, the …

We investigate the properties of the FLRW flat cosmological models in which the vacuum
energy density evolves with time, Λ (t). Using different versions of the Λ (t) model, namely …

Recently there have been claims of model-independent evidence of dynamical dark energy.
Herein we consider a fairly general class of cosmological models with a time-evolving …

Despite the many efforts, our theoretical understanding of the ultimate nature of the dark
energy component of the universe still lags well behind the astounding experimental …