Related papers: Scaling Dark Energy
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…
The conceptual difficulties associated with a cosmological constant have led to the investigation of alternative models in which the equation of state parameter, $w=p/\rho$, of the dark energy evolves with time. We show that combining the…
We show that the latest empirical constraints on cosmology, from a combination of DESI, CMB and supernova data, can be accounted for if a small component of dark matter has an evolving and oscillating equation of state within $-1<w<1$. From…
Theories of evolving quintessence are constructed that generically lead to deviations from the w = -1 prediction of non-evolving dark energy. The small mass scale that governs evolution, m_\phi \approx 10^{-33} eV, is radiatively stable,…
Observational evidence indicating that the expansion of the universe is accelerating has surprised cosmologists in recent years. Cosmological models have sought to explain this acceleration by incorporating `dark energy', of which the…
In this paper we investigate the epochs in which the Universe started accelerating and when it began to become dark energy-dominated (i.e., the dynamics of the expansion of the Universe dominated by the dark energy). We provide analytic…
Using the evolution history of the universe, one can make constraint on the parameter space of dynamic dark energy models. We discuss two different parameterized dark energy models. Our results further restrict the combined constraints…
Recent measurements suggest our universe has a substantial dark energy component, which is usually interpreted in terms of a cosmological constant. Here we examine how much the form of this dark energy can be modified while still retaining…
The property of dark energy and the physical reason for acceleration of the present universe are two of the most difficult problems in modern cosmology. The dark energy contributes about two-thirds of the critical density of the present…
The acceleration of the expansion of the universe has deep implications for structure formation, the composition of the universe, and its fate. Roughly 70% of the energy density is in a dark energy, whose nature remains unknown. Mapping the…
The time dependence of the dark energy density can be an important clue to the nature of dark energy in the universe. We show that future supernova data from dedicated telescopes (such as SNAP), when combined with data of nearby supernovae,…
We use data from observational cosmology to put constraints on higher-dimensional extensions of general relativity in which the effective four-dimensional dark-energy density (or cosmological "constant") decays with time. In particular we…
Dark energy and dark matter are the dominant sources in the evolution of the late universe. They are currently only indirectly detected via their gravitational effects, and there could be a coupling between them without violating…
We propose and investigate a class of dynamical dark energy models in which the cosmological constant evolves from negative values in the early Universe to a positive value at low redshifts. This framework includes a generalised ladder-step…
We present here some recent results concerning scalar-tensor Dark Energy models. These models are very interesting in many respects: they allow for a consistent phantom phase, the growth of matter perturbations is modified. Using a…
A finite vacuum energy density implies the existence of a UV scale for gravitational modes. This gives a phenomenological scale to the dynamical equations governing the cosmological expansion that must satisfy constraints consistent with…
Detecting dark energy dynamics is the main quest of current dark energy research. Addressing the issue demands a fully consistent analysis of CMB, large scale structure and SN-Ia data with multi-parameter freedom valid for all redshifts.…
The dynamics of expansion and large scale structure formation of the Universe are analyzed for models with dark energy in the form of a phantom scalar field which initially mimics a $\Lambda$-term and evolves slowly to the Big Rip…
The present work is an example of the application of the dynamical system analysis in the context of cosmology. Here cosmic evolution is considered in the background of homogeneous and isotropic flat Friedmann-Lema\^{i}tre-Robertson-Walker…
The accelerated expansion of the universe has now been confirmed by several independent observations including those of high redshift type Ia supernovae, and the cosmic microwave background combined with the large scale structure of the…