Here's a summary of the article on Black Hole Cosmology:

Black hole cosmology, also known as Schwarzschild cosmology, proposes that our observable universe is the interior of a black hole, originating as a "child universe" within a larger "parent universe." This model suggests that during the gravitational collapse of massive stars or galactic centers, matter reaches an extremely high but finite density, undergoes a "Big Bounce" rather than forming a singularity, and then rapidly expands to create a new universe on the other side of the black hole's event horizon.

The concept was initially proposed by Raj Pathria in 1972. More recently, in 2010, Nikodem Popławski provided a physically grounded mechanism for this process, based on the Einstein-Cartan theory of gravity. This theory incorporates torsion, generated by fermions, which prevents the formation of singularities and triggers the cosmic rebound, even leading to a period of exponential expansion similar to inflation. This intriguing scenario offers potential solutions to cosmological puzzles like the horizon and flatness problems, while also implying the existence of a grander multiverse.