Related papers: Phantom Fluid Cosmology -or- Ghosts for Gordon
Phantom scalar theories are widely considered in cosmology, but rarely at the quantum level, where they give rise to negative-energy ghost particles. These cause decay of the vacuum into gravitons and photons, violating observational…
It is known that theories of phantom dark energy, considered as quantum fields, predict a continuous production of positive- plus negative-energy particles, from spontaneous decay of the vacuum. We show that this can be a new source of…
Recent determinations of the equation of state of dark energy hint that this may well be of the phantom type, i.e., $w_{de} < -1$. If confirmed by future experiments, this would strongly point to the existence of fields that violate the…
We aim at the construction of dark energy models without exotic matter but with a phantom-like equation of state (an effective phantom phase). The first model we consider is decaying vacuum cosmology where the fluctuations of the vacuum are…
This paper is devoted to some simple approach based on general physics tools to describe the physical properties of a hypothetical particle which can be the source of dark energy in the Universe known as phantom. Phantom is characterized by…
We have investigated a cosmological model of a phantom energy with a variable cosmological constant ($\Lambda$) depending on the energy density ($\rho$) as $\Lambda\propto \rho^{-\alpha}$, $\alpha=\rm const.$ and a variable gravitational…
To explain the acceleration of the cosmological expansion researchers have considered an unusual form of mass-energy generically called dark energy. Dark energy has a ratio of pressure over mass density which obeys $w=p/\rho <-1/3$. This…
Phantom dark energy models, with w < -1, are characterized by a future singularity and therefore a finite lifetime for the universe. Because the future singularity is triggered by the onset of dark-energy domination, the universe spends a…
It has been suggested that a scalar field with negative kinetic energy, or ``ghost,'' could be the source of the observed late-time cosmological acceleration. Naively, such theories should be ruled out by the catastrophic quantum…
Recent attempts to explain the dark matter and energy content of the universe have involved some radical extensions of standard physics, including quintessence, phantom energy, additional space dimensions and variations in the speed of…
In this mini-review we discuss first why we should investigate cosmological models beyond LCDM. We then show how to describe dark energy or modified gravity models in a fluid language with the help of one background and two perturbation…
We investigate the possibility that part of the dark matter is not made out of the usual cold dark matter (CDM) dustlike particles, but is under the form of a fluid of strings with barotropic factor $w_s = -1/3$ of cosmic origin. To this…
Phantom dark energy is a proposal that explains the current observations that mildly favor the equation of state of dark energy $\omega^{de}$ crossing -1 at 68% confidence level. However, phantom fields are generally ruled out by…
We propose a dark energy model with a logarithmic cosmological fluid which can result in a very small current value of the dark energy density and avoid the coincidence problem without much fine-tuning. We construct a couple of dynamical…
Motivated by the apparent discrepancy between Cosmic Microwave Background measurements of the Hubble constant and measurements from Type-Ia supernovae, we construct a model for Dark Energy with equation of state $w = p / \rho < -1$,…
It is widely assumed that the observed universe is accelerating due to the existence of a new fluid component called dark energy. In this article, the thermodynamics consequences of a nonzero chemical potential on the dark energy component…
It has been suggested that the dark energy that explains the observed accelerating expansion of the universe may arise due to the contribution to the vacuum energy of the QCD ghost in a time-dependent background. The argument uses a…
In this letter we show that, at its fundamental level, phantom dark energy is a fluid made up of time crystals that permeate the fabric of space-time. In turn, any well-behaved stable theory of a non-canonical scalar field that acts as…
We review a dynamical dark energy model scarcely studied in the literature and we introduce two possible generalizations. We discuss separately the behavior of the original model and a minimal extension of it by exploring some early and…
It is extraordinary that a number of observations indicate that we live in a spatially flat, low matter density Universe, which is currently undergoing a period of accelerating expansion. The effort to explain this current state has focused…