Related papers: The Case for a Positive Cosmological Lambda-term
In order to solve the problem of eternal acceleration, a model has been recently proposed including both a negative cosmological constant $\Lambda$ and a scalar field evolving under the action of an exponential potential. We further explore…
We explore how local, cosmology-independent measurements of the Hubble constant and the age of the Universe help to provide a powerful consistency check of the currently favored cosmological model (flat LambdaCDM) and model-independent…
In this article the cosmological constant problems, as well as the astronomical evidence for a cosmologically significant homogeneous exotic energy density with negative pressure (quintessence), are reviewed for a broad audience of…
The cosmological term is assumed to be a function of time such as $\Lambda =Ba^{-2}$ where a(t) means the scale factor of standard cosmology. Analytical solutions for radiation dominated epoch and open universe are found. For closed…
The cosmological constant sets certain scales important in cosmology. We show that Lambda in conjunction with other parameters like the Schwarzschild radius leads to scales relevant not only for cosmological but also for astrophysical…
We focus on uncertainties in supernova measurements, in particular of individual magnitudes and redshifts, to review to what extent supernovae measurements of the expansion history of the universe are likely to allow us to constrain a…
Recently, there have been claims in the literature that the cosmological constant problem can be dynamically solved by specific compactifications of gravity from higher-dimensional toy models. These models have the novel feature that in the…
In order to deal with a large cosmological constant a relaxation mechanism based on modified gravity has been proposed recently. By virtue of this mechanism the effect of the vacuum energy density of a given quantum field/string theory (no…
We present a cosmographic study designed to test the simplest type of accelerating cosmology: a flat universe with matter and a cosmological constant ($\Lambda$). Hubble series expansions are fit to the SCP Union2.1 supernova data set to…
Supernovae observations strongly support the presence of a cosmological constant, but its value, which we will call apparent, is normally determined assuming that the Universe can be accurately described by a homogeneous model. Even in the…
The observed late-time acceleration of the Universe may be the result of unknown physical processes involving either modifications of gravitation theory or the existence of new fields in high energy physics. In the former case, such…
It is shown that the cosmological relativity theory prdicts the value Lambda = 1.934 x 10^-35 s^-2 for the cosmological constant. This value of Lambda is in exellent agreement with the measurements recently obtained by the High-Z Supernova…
The standard LambdaCDM cosmology passes demanding tests that establish it as a good approximation to reality. It is incomplete, with open questions and anomalies, but the same is true of all our physical theories. The anomalies in the…
We investigate some properties of flat cosmological models with a $\Lambda$ term that decreases with time as $\Lambda \propto a^{-m}$ (a is the scale factor and m is a parameter $0\leq m < 3$). The models are equivalent to standard…
A constant-rate creation of dark particles in the late-time FLRW spacetime provides a cosmological model in accordance with precise observational tests. The matter creation backreaction implies in this context a vacuum energy density…
Observation indicates that the expansion of the Universe is accelerating and favours a dynamical cosmological constant, \Lambda(t). We consider the possibility that this is due to a scalar field which has undergone a very recent phase…
The anthropic explanation for the peculiarly small observed value of the cosmological constant $\Lambda_{\rm obs}$ argues that this value promotes the formation of stars, planets, and ultimately of observers such as ourselves. I show that a…
The accelerating expansion of the universe is the most surprising cosmological discovery in many decades. In this short review, we briefly summarize theories for the origin of cosmic acceleration and the observational methods being used to…
We point out that the standard formulation of the cosmological constant problem itself is problematic since it is trying to apply the very large scale homogeneous cosmological model to very small (Planck) scale phenomenon. At small scales,…
We present a model that naturally tunes a large positive cosmological constant to a small cosmological constant. A slowly rolling scalar field decreases the cosmological constant to a small negative value, causing the universe to contract,…