Recently it was suggested that the dark energy maybe related to the well-known hierarchy between the Planck scale (∼ 10GeV) and the TeV scale. The same brane-world setup to address this hierarchy problem may also in principle address the smallness problem of dark energy. Specifically, the Planck-SM hierarchy ratio was viewed as a quantum gravity-related, dimensionless fine structure constant wh...

We describe a method to derive the expansion and acceleration rates directly from the data, without the need for the specification of a theory of gravity, and without adopting an a priori parameterization of the form or redshift evolution of the dark energy. If one also specifies a theory of gravity we can also determine the pressure, energy density, and equation of state of the dark energy as ...

Recent observations on Type-Ia supernovae and low density (Ωm = 0.3) measurement of matter including dark matter suggest that the presentday universe consists mainly of repulsive-gravity type ‘exotic matter’ with negative-pressure often said ‘dark energy’ (Ωx = 0.7). But the nature of dark energy is mysterious and its puzzling questions, such as why, how, where and when about the dark energy, a...

Our universe is observed to be accelerating due to the dominant dark energy with negative pressure. The dark energy equation of state (w) holds a key to understanding the ultimate fate of the universe. The cosmic voids behave like bubbles in the universe so that their shapes must be quite sensitive to the background cosmology. Assuming a flat universe and using the priors on the matter density ...

In this paper, we have studied a model of holographic dark energy (HDE) with homogeneous and anisotropic Bianchi type-I Universe in the framework Gauss-Bonnet (GB) gravity or $f(G)$ gravity. To find an exact solution field equations, assume that deceleration parameter varies cosmic time $\left( t\right) $. We plot some physical quantities give interpretations results obtained. Finally, compared...

Various TeVeS-inspired and f(R)-inspired theories of gravity have added an interesting twist to the search for dark matter and vacuum energy, modifying the landscape of astrophysics day by day. A common thread of various theories, according of an up-todate summary by HZL 1, is a non-uniform vector field, describing an uneven vacuum energy fluid. The so-called ”alternative” gravity theories are ...