Related papers: Quintessence and the accelerating universe
The cosmological model best capable of fitting current observational data features two separate epochs during which the Universe is accelerating. During the earliest stages of the Universe, such acceleration is known as cosmological…
Cosmologists are just beginning to probe the properties of the cosmic vacuum and its role in reversing the attractive pull of gravity to cause an acceleration in the expansion of the cosmos. The cause of this acceleration is given the…
A nonminimally coupled hybrid dark energy model is introduced. The dark energy evolution is triggered by mass varying neutrinos. Quintessence evolution begins from an initial point, with an insignificant dark energy density, and arrives at…
The origin of the observed acceleration of the expansion of the universe is a major problem of modern cosmology and theoretical physics. Simple estimations of the contribution of vacuum to the density energy of the universe in quantum field…
We propose a cosmological model that makes a significant step toward solving the coincidence problem of the near similarity at the present of the dark energy and dark matter components. Our cosmology has the following properties: a) among…
One of the great endeavors of the past decade has been the evaluation of different observational techniques for measuring dark energy properties and of theoretical techniques for constraining models of cosmic acceleration given cosmological…
I briefly review the cosmological constant problem and the issue of dark energy (or quintessence). Within the framework of quantum field theory, the vacuum expectation value of the energy momentum tensor formally diverges as $k^4$. A cutoff…
The principles of General Relativity allow for a non-vanishing cosmological constant, which can possibly be interpreted at least partially in terms of quantum-fluctuations of matter fields. Depending on sign and magnitude it can cause…
We have observed the acceleration of the expansion of the universe. To explain this phenomenon, we usually introduce the dark energy (DE) which has a negative pressure or we need to modify the Einstein's equation to produce a term which is…
A ghost dark energy model has been recently put forward to explain the current accelerated expansion of the Universe. In this model, the energy density of ghost dark energy, which comes from the Veneziano ghost of QCD, is proportional to…
2017 observations by Riess and coworkers have indicated that the universe is expanding some seven percent faster than the currently accepted cosmological model described. In this paper we argue that this discrepancy can be eliminated by…
In this work we perform some studies related to dark energy. Firstly, we propose a dynamical approach to explain the dark energy content of the universe. We assume that a massless scalar field couples to the Hubble parameter with some…
Cosmic acceleration is explained quantitatively, as an apparent effect due to gravitational energy differences that arise in the decoupling of bound systems from the global expansion of the universe. "Dark energy" is a misidentification of…
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…
Dark energy, the main constituent in our expanding universe, responsible for its acceleration, is currently being observed with unprecedented precision through various experiments. While several cosmological models can fit this latest data,…
The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational…
Recent observations of the Universe have led to a conclusion suppressing an up-to-now supposed deceleration of the Universe caused by attractive gravitational forces. Contrary, there is a renaissance of the cosmological member lambda and…
The presence of dark energy in the Universe is inferred directly and indirectly from a large body of observational evidence. The simplest and most theoretically appealing possibility is the vacuum energy density (cosmological constant).…
Dark energy in the universe is assumed to be vacuum energy. The energy-momentum of vacuum is described by a scale-dependent cosmological constant. The equations of motion imply for the density of matter (dust) the sum of the usual matter…
The acceleration of the universe is described as a dynamical effect of the extrinsic curvature of space-time. By extending previous results, the extrinsic curvature is regarded as an independent spin-2 field, determined by a set of…