Related papers: Can dark energy evolve to the Phantom?
Cosmological observations strongly suggest the presence of dark energy which comprises the majority of the current energy density of the universe. The equation of state relating the pressure and energy density of this dark energy, p = w…
Two new one-parameter tracking behavior dark energy representations $\omega=\omega_0/(1+z)$ and $\omega=\omega_0 e^{z/(1+z)}/(1+z)$ are used to probe the geometry of the Universe and the property of dark energy. The combined type Ia…
The observational effect of all minimally coupled scalar field models of dark energy can be determined by the behavior of the following two parameters : (1) equation of state parameter $w$, which relates dark energy pressure to its energy…
We suggest that the current acceleration of the universe may be explained by the vacuum energy of a hidden sector which is stuck in a state of equilibrium between phases. The phases are associated to a late-time first-order phase…
Rolling tachyon field models are among the candidates suggested as explanations for the recent acceleration of the Universe. In these models the field is expected to interact with gauge fields and lead to variations of the fine-structure…
I consider a scenario proposed by Fardon, Nelson and Weiner where dark energy and neutrinos are connected. As a result, neutrino masses are not constant but depend on the neutrino number density. By examining the full equation of state for…
We examine a dark energy model where a scalar unparticle degree of freedom plays the role of quintessence. In particular, we study a model where the unparticle degree of freedom has a standard kinetic term and a simple mass potential, the…
Current cosmological observations show a strong signature of the existence of a dark energy component with negative pressure. The most obvious candidate for this dark energy is the cosmological constant (with the equation of state…
In this talk I will firstly review on the current constraints on the equation of state of the dark energy from observational data, then present a new scenario of dark energy dubbed {\it Quintom}. The recent fits to the type Ia supernova…
Stability analysis of agegraphic dark energy in Brans-Dicke theory is presented in this paper. We constrain the model parameters with the observational data and thus the results become broadly consistent with those expected from experiment.…
Dark energy dynamics in the recent universe is influenced by its evolution through the long, matter dominated expansion history. A particular dynamical property, the flow variable, remains constant in several classes of scalar field models…
In this paper we consider a spatially flat Friedmann-Robertson-Walker (FRW) cosmological model whit cosmological constant, containing a stiff fluid and a classical Dirac field. The proposed cosmological scenario describes the evolution of…
Many ambitious experiments have been proposed to constrain dark energy and detect its evolution. At present, observational constraints are consistent with a cosmological constant and there is no firm evidence for any evolution in the dark…
If the dark energy equation of state parameter w(z) crosses the phantom divide line w=-1 (or equivalently if the expression d(H^2(z))/dz - 3\Omega_m H_0^2 (1+z)^2 changes sign) at recent redshifts, then there are two possible cosmological…
Recent supernovae of type Ia measurements and other astronomical observations suggest that our universe is in accelerating phase of evolution at the present epoch. While a dark energy of unknown form is usually proposed as the most feasible…
The cosmic acceleration is one of the most significant cosmological discoveries over the last century. Following the more accurate data a more dramatic result appears: the recent analysis of the observation data (especially from SNe Ia)…
A physical mechanism that produces three energy components is proposed as the common origin of dark energy and dark matter. The first two have equations of state W ~ 0 and act like dark matter, while the last has W ~ -1 at low redshifts…
We consider a brane cosmological model with energy exchange between brane and bulk. Parameterizing the energy exchange term by the scale factor and Hubble parameter, we are able to exactly solve the modified Friedmann equation on the brane.…
One of the most important and surprising discoveries in cosmology in recent years is the realization that our Universe is dominated by a mysterious dark energy, which leads to an accelerating expansion of space-time. A simple generalization…
We investigate several varying-mass dark-matter particle models in the framework of phantom cosmology. We examine whether there exist late-time cosmological solutions, corresponding to an accelerating universe and possessing dark energy and…