In this paper we introduce the fractional dark energy model, in which accelerated expansion of Universe is driven by a nonrelativistic gas (composed either fermions or bosons) with noncanonical kinetic term. The inversely proportional to cube absolute value momentum for fluid an equation state parameter equal minus one, and whose corresponding density mimics one cosmological constant. general c...

We investigate the clustering properties of dynamical Dark Energy even in association of a possible coupling between Dark Energy and Dark Matter. We find that within matter inhomogeneities, Dark Energy migth form voids as well as overdensity depending on how its background energy density evolves. Consequently and contrarily to what expected, Dark Energy fluctuations are found to be slightly sup...

A long-standing problem of theoretical physics is the exceptionally small value of the cosmological constant Λ ∼ 10−120 measured in natural Planckian units. Here we derive this tiny number from a toroidal string cosmology based on closed strings. In this picture the dark energy arises from the correlation between momentum and winding modes that for short distances has an exponential fall-off wi...

In this paper, we give a conceptual explanation of dark energy as a small negative residual scalar curvature present even in empty spacetime. This curvature ultimately results from postulating a discrete spacetime geometry, very closely related to that used in the dynamical triangulations approach to quantum gravity. In this model, there are no states which have total scalar curvature exactly z...

Most of the models leading to a current state of cosmic accelerated expansion fail to address the coincidence problem, i.e., that the dark energy density and the energy density of the matter fluid are of the same order precisely today. We show that a way to drive late acceleration and simultaneously solve the aforesaid problem is assuming the matter fluid dissipative [1]. 1 General setting The ...

In the Randall-Sundrum scenario we analyze the dynamics of an AdS5 braneworld when conformal matter fields propagate in 5-dimensions. We show that conformal fields of weight −4 are associated with stable geometries which describe the dynamics of inhomogeneous dust, generalized dark radiation and homogeneous polytropic dark energy on a spherically symmetric 3-brane embedded in the compact AdS5 o...

The physical origin of holographic dark energy (HDE) is investigated. The main existing explanations, namely the UV/IR connection argument of Cohen et al, Thomas’ bulk holography argument, and Ng’s spacetime foam argument, are shown to be not satisfactory. A new explanation of the HDE model is then proposed based on the ideas of Thomas and Ng. It is suggested that the dark energy might originat...

We explore the fate of the universe given the possibility that the density associated with ‘dark energy’ may decay slowly with time. We model decaying dark energy by a homogeneous scalar field which couples minimally to gravity and whose potential has at least one local maximum. Dark energy decays as the scalar field rolls down its potential and this allows for several interesting possibilities...