The apparent (gravitational) horizon in cosmology

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

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 state of the cosmic fluid. In this paper, we examine how and why an apparent (gravitational) horizon is manifested in the Friedmann-Robertson-Walker metric, and why it is becoming so pivotal to our correct interpretation of the cosmological data. We discuss its observational signature and demonstrate how it alone defines the proper size of our visible Universe. In so doing, we affirm its physical reality and its impact on cosmological models.

Original languageEnglish (US)
Pages (from-to)585-593
Number of pages9
JournalAmerican Journal of Physics
Volume86
Issue number8
DOIs
StatePublished - Aug 1 2018

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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