What are some specific topics pertaining to black holes?

Personally, I think that one of the most interesting aspects of black holes is the theoretical Einstein-Rosen Bridge. It was a proposed theory about the possibility of two black holes conjoining at a throat that could join two distant points in space or even two entirely different universes. You could research this topic and some of its applications for space or interdimensional travel or even time travel; you could even research some of the theoretical ways for "wormhole" stabilization.