A peek outside our universe

Enrique Gaztanaga*, Pablo Fosalba

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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According to general relativity (GR), a universe with a cosmological constant ΛΛ, like ours, is trapped inside an event horizon, 𝑟<3/Λ−−−−√�<3/Λ. What is outside? We show, using Israel (1967) junction conditions, that there could be a different universe outside. Our universe looks like a black hole for an outside observer. Outgoing radial null geodesics cannot escape our universe, but incoming photons can enter and leave an imprint on our CMB sky. We present a picture of such a fossil record from the analysis of CMB maps that agrees with the black hole universe predictions but challenges our understanding of the origin of the primordial universe.
Original languageEnglish
Article number285
Number of pages6
Issue number2
Publication statusPublished - 31 Jan 2022


  • Black holes
  • Cosmology
  • Dark energy
  • General relativity

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