# The cosmic horizon

@article{Melia2007TheCH, title={The cosmic horizon}, author={Fulvio Melia}, journal={Monthly Notices of the Royal Astronomical Society}, year={2007}, volume={382}, pages={1917-1921} }

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 from an application of this metric to the Einstein Field Equations describe the expansion of the Universe in terms of comoving coordinates, from which physical distances may be derived using a time-dependent expansion factor. These coordinates, however, do not explicitly reveal the properties of… Expand

#### 113 Citations

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

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- 2009

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… Expand

The cosmic equation of state

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- 2014

The cosmic spacetime is often described in terms of the Friedmann-Robertson-Walker (FRW) metric, though the adoption of this elegant and convenient solution to Einstein’s equations does not tell us… Expand

Physical basis for the symmetries in the Friedmann–Robertson–Walker metric

- Physics
- 2016

Modern cosmological theory is based on the Friedmann–Robertson–Walker (FRW) metric. Often written in terms of co-moving coordinates, this well-known solution to Einstein’s equations owes its elegant… Expand

The gravitational horizon for a Universe with phantom energy

- Physics
- 2012

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… Expand

THE COSMOLOGICAL SPACETIME

- Physics
- 2009

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… Expand

A Cosmological Basis for E = mc 2

- Physics
- 2019

The Universe has a gravitational horizon with a radius R_h=c/H coincident with that of the Hubble sphere. This surface separates null geodesics approaching us from those receding, and as free-falling… Expand

Proper size of the visible Universe in FRW metrics with a constant spacetime curvature

- Physics, Mathematics
- 2013

In this paper, we continue to examine the fundamental basis for the Friedmann–Robertson–Walker (FRW) metric and its application to cosmology, specifically addressing the question: What is the proper… Expand

Photon geodesics in Friedmann–Robertson–Walker cosmologies

- Physics
- 2012

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.… Expand

Cosmological consequences of theories of modified gravity

- Physics
- 2018

Our theoretical understanding of the dynamical evolution of the Universe has certainly improved during the recently established era of precision cosmology. However, the nature of the dark sector… Expand

The Rh=ct universe

- Physics
- 2011

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… Expand

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I am writing with a simple plea to balance the voluminous articles about treatment in your journal with a modicum of information about nature and caring effects to rekindle the perception of physicians as healers, not only treaters, who relish the gifts of nature, and foster the humanistic aspect of medicine that has thrived for millennia. Expand