The discussion centers on the theoretical possibility of a smaller black hole existing within the event horizon of a larger black hole. It concludes that while a smaller black hole cannot orbit inside a larger black hole's event horizon, a swarm of stars can temporarily exist within its own Schwarzschild Radius. The conversation highlights the complexities of defining horizons in such scenarios, emphasizing the need for different definitions, such as a "future outer trapping horizon." The implications of gravitational time dilation and the behavior of black holes in relation to general relativity are also explored.
PREREQUISITESAstronomers, physicists, and students of theoretical physics interested in advanced black hole dynamics and the complexities of general relativity.
hurk4 said:Unless someone is inside a BH??
Haelfix said:The problem with having a black hole inside a black hole is several fold.
Xantox is right, there is a problem with the horizon definition.
Worse, there is a problem with the asymptotics. The asymptotics of the interior black hole/star solution does not have minkowski space as a limit, so the very metric itself is poorly joined. In fact, it has some god awful time varying thing as an asymptote.
The problem has indeed been looked at before, and its apparently one of the most excruciatingly complex things to do numerically in all of physics. The last time I talked with someone about it (I believe the state of the art is in Germany), they're still in rarefied extremal D != 4 situations with a bunch of highly technical assumptions which would take a specialist to explain, and even then, the computer returns junk most of the time.