Black Holes and Relativistic Jets

There is strong observational evidence that AGN, Galactic X-ray transientsand (probably) $\gamma$-ray bursts are associated with black holes, and thatthese sources are able to form collimated, ultrarelativistic outflows. There ismuch interest in trying to understand how these prime movers are able torelease energy from accreting gas and their own spin energy. Electromagneticfield plays a large role in many of the mechanisms under active consideration.In this article, several of the many possible ``metabolic pathways'' throughwhich mass, angular momentum and energy can flow around and away from blackhole magnetospheres are discussed. Particular importance is attached to theinteractions between the inflowing disk, the outflowing wind, the black holeand the jet. Some important unresolved questions are identified and it isargued that large scale numerical computation will almost certainly benecessary to address them.Comment: 21 pages Progress of Theoretical Physics Supplement in pres