The simplest ΛCDM model provides a good fit to a large span of cosmological data but
harbors large areas of phenomenology and ignorance. With the improvement of the number …

It is well known that quantum field theory (QFT) induces a huge value of the cosmological
constant (CC), Λ, which is outrageously inconsistent with cosmological observations. We …

Recent observations of Type 1a supernovae indicating an accelerating universe have once
more drawn attention to the possible existence, at the present epoch, of a small positive Λ …

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 …

We investigate the coupled system of gravity and a scalar with exponential potential. The
energy momentum tensor of the scalar field induces a time-dependent cosmological`` …

We review the general features of nonsingular universes (ie those that go from an era of
accelerated collapse to an expanding era without displaying a singularity) as well as cyclic …

We show that a general late-time interaction between cold dark matter and vacuum energy
is favored by current cosmological data sets. We characterize the strength of the coupling by …

A substantial body of phenomenological and theoretical work over the last few years
strengthens the possibility that the vacuum energy density (VED) of the universe is …

The evolution of the scale factor a (t) in Friedmann models (those with zero pressure and a
constant cosmological term Λ) is well understood, and elegantly summarized in the review of …

Despite the fact that a rigid ${\rm {\Lambda}} $-term is a fundamental building block of the
concordance ΛCDM model, we show that a large class of cosmological scenarios with …