A peek outside our Universe

Abstract

According to general relativity (GR), a universe with a cosmological constant $\Lambda$, like ours, is trapped inside an event horizon, $r<\sqrt{3/\Lambda }$. 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.

arXiv comment3 pages. Essay written for the Gravity Research Foundation 2021 Awards for Essays on Gravitation

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Cited by in corpus (2)

• A measurement of the scale of homogeneity in the Early Universe
• On the Dynamical Instability of Monatomic Fluid Spheres in (N+1)-Dimensional Spacetime