Related papers: Gravitational vacuum energy in our recently accele…
Observations conducted over the last few decades show that the expansion of the Universe is accelerating. In the standard model of cosmology, this accelerated expansion is attributed to a dark energy in the form of a cosmological constant.…
An expanding universe is not expected to have a static vacuum energy density. The so-called cosmological constant $\Lambda$ should be an approximation, certainly a good one for a fraction of a Hubble time, but it is most likely a temporary…
We investigate the gravitational property of the quantum vacuum by treating its large energy density predicted by quantum field theory seriously and assuming that it does gravitate to obey the equivalence principle of general relativity. We…
In order to explain the Late-times accelerated expansion of the Universe we must appeal to some form of Dark Energy. In the standard model of cosmology, the latter is interpreted as a Cosmological Constant $\Lambda$. However, for a number…
We review the evidence for recently accelerating cosmological expansion or "dark energy", either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity), without any Dark Energy constituent. If…
Physics invites the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant, Lambda; nowadays the concept is termed dark energy or quintessence. Physics also suggests the dark energy…
The $\Lambda$CDM framework offers a remarkably good description of our universe with a very small number of free parameters, which can be determined with high accuracy from currently available data. However, this does not mean that the…
The current expansion of the Universe has been observed to be accelerating, and the widely accepted spatially-flat concordance model of general relativistic cosmology attributes this phenomenon to a constant dark energy, a cosmological…
A type of exponential correction to General Relativity gives viable modified gravity model of dark energy. The model behaves as $R-2\Lambda$ at large curvature where an effective cosmological constant appears, but it becomes zero in flat…
Major observational efforts in the coming decade are designed to probe the equation of state of dark energy. Measuring a deviation of the equation-of-state parameter w from -1 would indicate a dark energy that cannot be represented solely…
The canonical cosmological model to explain the recent acceleration of the universe relies on a cosmological constant, and most dynamical dark energy and modified gravity model alternatives are based on scalar fields. Still, further…
The homogeneous expansion history H(z) of our universe measures only kinematic variables, but cannot fix the underlying dynamics driving the recent acceleration: cosmographic measurements of the homogeneous universe, are consistent with…
Within the $\Lambda$CDM cosmological model, the absolute value of Einstein's cosmological constant $\Lambda$, sometimes expressed as the gravitating mass-energy density $\rho_\Lambda$ of the physical vacuum, is a fundamental constant of…
We use all available baryon acoustic oscillation distance measurements and Hubble parameter data to constrain the cosmological constant $\Lambda$, dynamical dark energy, and spatial curvature in simple cosmological models. We find that the…
The expansion rate of the Universe changes with time, initially slowing (decelerating) when the universe was matter dominated, because of the mutual gravitational attraction of all the matter in it, and more recently speeding up…
Recent measurements of the parameters of the Concordance Cosmology Model ($\Lambda$CDM) done in the low-redshift Universe with Supernovae Ia/Cepheids, and in the distant Universe done with Cosmic Microwave Background (CMB) imply different…
Perhaps the deepest mystery of our accelerating Universe in expansion is the existence of a tiny and rigid cosmological constant, $\Lambda$. Its size is many orders of magnitude below the expected one in the standard model of particle…
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}}…
The current standard cosmological model is constructed within the framework of general relativity with a cosmological constant $\Lambda$, which is often associated with dark energy, and phenomenologically explains the accelerated cosmic…
In the $\Lambda$CDM model, dark energy is viewed as a constant vacuum energy density, the cosmological constant in the Einstein--Hilbert action. This assumption can be relaxed in various models that introduce a dynamical dark energy. In…