The more mass you add to a black hole the lighter it gets until according to some a black hole the size of our universe would have the same average density as our universe. And it turns out that adding mass to a black hole increases their radius much quicker than was previously presumed
Well a black hole is super hot on the inside right? Not only super hot at the edge, its super cold on the inside:
What if you wanted to simulate the universe?
A black hole is probably your best bet. See the Black Brane stuff from Greene’s Hidden Reality book also touched upon in the Joe Armstrong thread where Armstrong talks about a paper done by Seth Lloyde.
The idea of the universe simulated on a black hole seemed a bit strange but if you model the physics of the inside of a black hole with super symmetry and the surface with quantum gravity the two seemingly mutually exclusive theories come together and difficult problems to solve from or approach or the other suddenly fluidly translate.