The gravitational horizon for a Universe with phantom energy

@article{Melia2012TheGH,
  title={The gravitational horizon for a Universe with phantom energy},
  author={Fulvio Melia},
  journal={Journal of Cosmology and Astroparticle Physics},
  year={2012},
  volume={2012},
  pages={029-029}
}
  • F. Melia
  • Published 27 June 2012
  • Physics
  • Journal of Cosmology and Astroparticle Physics
The Universe has a gravitational horizon, coincident with the Hubble sphere, that plays an important role in how we interpret the cosmological data. Recently, however, its significance as a true horizon has been called into question, even for cosmologies with an equation-of-state w≡p/ρ ≥ −1, where p and ρ are the total pressure and energy density, respectively. The claim behind this argument is that its radius Rh does not constitute a limit to our observability when the Universe contains… 

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References

SHOWING 1-10 OF 25 REFERENCES

The cosmic horizon

The cosmological principle, promoting the view that the Universe is homogeneous and isotropic, is embodied within the mathematical structure of the Robertson‐Walker (RW) metric. The equations derived

CONSTRAINTS ON DARK ENERGY FROM THE OBSERVED EXPANSION OF OUR COSMIC HORIZON

Within the context of standard cosmology, an accelerating universe requires the presence of a third "dark" component of energy, beyond matter and radiation. The available data, however, are still

How does the Hubble sphere limit our view of the Universe

It has recently been claimed that the Hubble sphere represents a previously unknown limit to our view of the universe, with light we detect today coming from a proper distance less than this ‘cosmic

Photon geodesics in Friedmann–Robertson–Walker cosmologies

The Hubble radius is a particular manifestation of the Universe’s gravitational horizon, Rh(t0) ≡c/H0, the distance beyond which physical processes remain unobservable to us at the present epoch.

The Rh=ct universe

The backbone of standard cosmology is the Friedmann-Robertson-Walker solution to Einstein's equations of general relativity (GR). In recent years, observations have largely confirmed many of the

Scalar–tensor models of normal and phantom dark energy

We consider the viability of dark energy (DE) models in the framework of the scalar–tensor theory of gravity, including the possibility of having a phantom DE at small redshifts z as admitted by

THE COSMOLOGICAL SPACETIME

We present here the transformations required to recast the Robertson–Walker metric and Friedmann–Robertson–Walker equations in terms of observer-dependent coordinates for several commonly assumed

Through the looking glass: why the 'cosmic horizon' is not a horizon

The present standard model of cosmology, Λ cold dark matter (ΛCDM), contains some intriguing coincidences. Not only are the dominant contributions to the energy density approximately of the same

Detecting dark energy in orbit: The cosmological chameleon

We show that the chameleon scalar field can drive the current phase of cosmic acceleration for a large class of scalar potentials that are also consistent with local tests of gravity. These provide