Our Universe as a Black Hole in a Larger Space

<p>Using present day estimates of the size and average density of the observable universe, its Schwarzschild radius is found to exceed its physical radius. This means that, if the observable universe is a representative part of a material universe included in a larger space, this material universe should be a black hole.Approximating the material universe by a sphere filled with pressure-less gas of uniform density, its geometry is described by a piece of Friedmann-Lemaître-Robertson-Walker metric embedded in a Schwarzschild metric.The matching of the two metrics at the surface of the material sphere sets the boundary conditions for the interior part.Mathematically, the equation relating the proper time to the coordinate time in the interior of the black hole has two solutions of opposite signs. If the negative solution is adopted, matter collapsing towards the singularity is perceived as expanding by observers inside the black hole. This allows to reconcile the facts that we observe an expanding universe while we should be inside a black hole. The proper time being the one that controls the physical processes, the physics inside the black hole universe is the same as in the usual expanding universe models. However, a fundamental change concerns the boundary conditions: the latter are not set at the singularity but at the start of the collapse, in our far future. Such a change of boundary conditions allows to propose a solution to three fundamental problems of the Big Bang cosmology: the horizon problem, the flatness problem and the particle-antiparticle asymmetry.</p>