Related papers: The Cosmic Coincidence Problem in the Brane World
An interaction between dark matter and dark energy is usually introduced by a phenomenological modification of the matter conservation equations, while the Einstein equations are left unchanged. Starting from some general and fundamental…
We examine the embedding of dark energy in high energy models based upon supergravity and extend the usual phenomenological setting comprising an observable sector and a hidden supersymmetry breaking sector by including a third sector…
We discuss the coupling between dark energy and matter by considering a homogeneous tachyonic scalar field as a candidate for dark energy. We obtained the functional form of scale factor by assuming that the coupling strength depends…
In brane-world models with low tension, massive branons are natural candidates for dark matter. The phenomenology of these WIMP-like particles is completely determined by their mass, the brane tension and, in the case of effects due to…
(Abridged) Present cosmological constraints and the absence of a direct detection and identification of any dark matter particle candidate leave room to the possibility that the dark sector of the Universe be actually more complex than it…
The interaction between Dark Matter and Dark Energy has been proposed as a mechanism to alleviate the coincidence problem. We analyze the effect of the interaction on the evolution of the gravitational field and propose two new observables…
We perform a detailed phase-space analysis of various phantom cosmological models, where the dark energy sector interacts with the dark matter one. We examine whether there exist late-time scaling attractors, corresponding to an…
In this work we review briefly the origin and history of the cosmological constant and its recent reincarnation in the form of the dark energy component of the universe. We also comment on the fundamental problems associated to its…
We demonstrate that a scalar field is unable to reverse its direction of motion while continuously exchanging energy with another fluid. If the rate of transfer is modulated by the scalar's acceleration, the field can undergo a rapid…
We consider a scenario where dark energy and baryons are dynamically coupled without any energy transfer. In this scenario, the background cosmology is unaffected and, at the perturbations level, the coupling only appears through the…
Some issues of the cosmological constant or dark energy are briefly reviewed. There are an increasing number of observations that constrain the equation of state of dark energy more stringently and favor the time-independent cosmological…
The recent high-quality Boomerang data allow to test many competing cosmological models. Here I present a seven-parameter likelihood analysis of dark energy models with exponential potential and explicit coupling to dark matter. Such a…
We present some cosmological solutions of Brans-Dicke theory, characterized by a decaying vacuum energy density and by a constant relative matter density. With these features, they shed light on the cosmological constant problems, leading…
While observational cosmology has shown tremendous growth over the last decade, deep mysteries continue to haunt our theoretical understanding of the ingredients of the concordance cosmological model, which are mainly `dark'. More than 95…
The observational relation between the density of baryon and dark matter in the Universe, $\Omega_{\rm DM}/\Omega_B\simeq 5$, is one of the most difficult problems to solve in modern cosmology. We discuss a scenario that explains this…
We explore the physics of a gas of particles interacting with a condensate that spontaneously breaks Lorentz invariance. The equation of state of this gas varies from 1/3 to less than -1 and can lead to the observed cosmic acceleration. The…
The discovery of the accelerating universe indicates strongly the presence of a scalar field which is not only expected to solve today's version of the cosmological constant problem, or the fine-tuning and the coincidence problems, but also…
By assuming a phenomenological form for the ratio of the DE and DM densities $\rho_X\propto \rho_{m} a^{\xi}$ (Dalal et al.2001), we discuss the cosmic coincidence problem in light of current observational data. $\xi$ is a key parameter to…
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…
The existence of dark energy is essential to explain the cosmic accelerated expansion. We consider a homogenous interacting tachyonic scalar field as a possible candidate for the dynamical dark energy. The interaction between the tachyonic…