The apparent (gravitational) horizon in cosmology

  title={The apparent (gravitational) horizon in cosmology},
  author={Fulvio Melia},
  journal={American Journal of Physics},
  • F. Melia
  • Published 19 July 2018
  • Physics
  • American Journal of Physics
In general relativity, a gravitational horizon (more commonly known as the “apparent horizon”) is an imaginary surface beyond which all null geodesics recede from the observer. The Universe has an apparent (gravitational) horizon, but unlike its counterpart in the Schwarzschild and Kerr metrics, it is not static. It may eventually turn into an event horizon—an asymptotically defined membrane that forever separates causally connected events from those that are not—depending on the equation of… 

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