Related papers: What Drives Our Accelerating Universe?
Homogeneous cosmological solutions are obtained in five dimensional space time assuming equations of state $ p = k\rho $ and $ p_{5}= \gamma\rho$ where p is the isotropic 3 - pressure and $p_{5}$, that for the fifth dimension. Using…
A huge amount of good quality astrophysical data converges towards the picture of a spatially flat universe undergoing the today observed phase of accelerated expansion. This new observational trend is commonly addressed as Precision…
Non-negligible dark energy density at high redshifts would indicate dark energy physics distinct from a cosmological constant or ``reasonable'' canonical scalar fields. Such dark energy can be constrained tightly through investigation of…
The universe appears to be accelerating, but the reason why is a complete mystery. The simplest explanation, a small vacuum energy (cosmological constant), raises three difficult issues: why the vacuum energy is so small, why it is not…
The accelerated expansion of the Universe is impressively well described by a cosmological constant. However, the observed value of the cosmological constant is much smaller than expected based on quantum field theories. Recent efforts to…
In this work, I develop an alternative explanation for the acceleration of the cosmic expansion, which seems to be a result of recent high redshift Supernova data. In the current interpretation, this cosmic acceleration is explained by…
It is commonly stated that we have entered the era of precision cosmology in which a number of important observations have reached a degree of precision, and a level of agreement with theory, that is comparable with many Earth-based physics…
Recent data advances offer the exciting prospect of a first look at whether dark energy has a dynamical equation of state or not. While formally theories exist with a constant equation of state, they are nongeneric -- Einstein's…
Dark energy is a fundamental constituent of our universe, its status in the cosmological field equation should be equivalent to that of gravity. Here we construct a dark energy and matter gravity coupling (DEMC) model of cosmology in a way…
The acceleration of the cosmic expansion revealed by supernova observations indicates that the present universe is dominated by repulsive dark energy. It is natural that the coupling between the dark energy and the attractive gravity has to…
In this colloquium-level account, I describe the cosmological constant problem: why is the energy of empty space at least 60 orders of magnitude smaller than several known contributions to it from the Standard Model of particle physics? I…
Dynamical dark energy (DE) has been proposed to explain various aspects of the cosmological constant (CC) problem(s). For example, it is very difficult to accept that a strictly constant Lambda-term constitutes the ultimate explanation for…
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…
The effective evolution of an inhomogeneous universe model in any theory of gravitation may be described in terms of spatially averaged variables. In Einstein's theory, restricting attention to scalar variables, this evolution can be…
The physical process leading to the acceleration of the expansion of the universe is unknown. It may involve new high energy physics or extensions to gravitation. Calling this generically dark energy, we examine the consistencies and…
Vacuum energy is a simple model for dark energy driving an accelerated expansion of the universe. If the vacuum energy is inhomogeneous in spacetime then it must be interacting. We present the general equations for a spacetime-dependent…
Since its decovery during the late 90's, the dimming of distant SN Ia apparent luminosity has been mostly ascribed to the influence of a mysterious dark energy component. Based upon the cosmological "principle" hypothesis, this…
Possibly the most peculiar expectation of the standard fine-tuned cosmological paradigm is that cosmic acceleration is to only be a very recent (z<1) phenomenon, with the universe being required to be decelerating at all higher redshifts.…
Astronomical observations strongly suggest that our universe is now accelerating and contains a substantial admixture of dark vacuum energy. Using numerical simulations to study this newly consolidated cosmological model (with a constant…
The standard formulation of the cosmological constant problem is based on one critical assumption---the spacetime is homogeneous and isotropic, which is true only on cosmological scales. However, this problem is caused by extremely small…