# A Peek Outside Our Universe

@article{Gaztaaga2022APO, title={A Peek Outside Our Universe}, author={Enrique Gazta{\~n}aga and Pablo Fosalba}, journal={Symmetry}, year={2022}, volume={14}, pages={285} }

According to general relativity (GR), a universe with a cosmological constant Λ, like ours, is trapped inside an event horizon, r<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…

## 5 Citations

### The Cosmological Constant as Event Horizon

- PhysicsSymmetry
- 2022

General Relativity allows for a cosmological constant (Λ) which has inspired models of cosmic Inflation and Dark Energy. We show instead that rΛ=3/Λ corresponds to an event horizon: a causal boundary…

### How the Big Bang end up inside a Black Hole

- Physics
- 2022

: The standard model of cosmology assumes that our Universe began 14 Gyrs (billion years) ago with a hot Big Bang expansion out of nothing. It can explain a vast range of different astrophysical data…

### How the Big Bang End Up Inside a Black Hole

- PhysicsUniverse
- 2022

The standard model of cosmology assumes that our Universe began 14 Gyrs (billion years) ago with a hot Big Bang expansion out of nothing. It can explain a vast range of different astrophysical data…

### A measurement of the scale of homogeneity in the early Universe

- PhysicsJournal of Cosmology and Astroparticle Physics
- 2022

We present the first measurement of the homogeneity index, ℋ, a fractal or Hausdorff dimension of the early Universe from the Planck CMB temperature variations δT in the sky. This characterization of…

### On the Dynamical Instability of Monatomic Fluid Spheres in (N+1)-dimensional Spacetime

- Physics
- 2021

In this note, I derive the Chandrasekhar instability of a ﬂuid sphere in ( N +1)-dimensional Schwarzschild-Tangherlini spacetime and take the homogeneous (uniform energy density) solution for…

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