Fusion research is usually grouped under plasma physics. Not all universities do fusion research, and some do it but not in the physics department (say, the Applied Physics department, or Nuclear Engineering department), so be sure to look beyond just the physics department's website. Only the bigger universities have actual working fusion reactors; smaller departments are usually left to do theory (or maybe plasma experiments). If you haven't seen it, here's a decent resource for learning about fusion and seeing where research is being done: http://fusedweb.llnl.gov/sites.html
Also, for what it's worth, some people will say that fusion research is dying and that it will never pan out as an energy source, but I don't see it as being that bad of a field to go into. For one, I think interest will be growing over the next few years, between the NIF and ITER projects. Also, plasmas have a lot of other useful applications, so even if fusion doesn't really work out, it's not like you'd suddenly have a useless specialty. But hey, what do I know?
As for your other two interests: they do seem a bit out there
. If you are really interested in gravity, you might want to look into general relativity. That always seems to be the field that comes up whenever people talk about wormholes and theoretical warp drives and such, although I've heard no indications that anyone is working on manipulating gravity. I don't know if such a thing is even theoretically possible. But who knows? Can't hurt to look into it. As for your third interest, I really couldn't say. I'm not even sure what area it would fall under.
I'm sorry, I know I talked more about fusion than the other two topics, but that's cause I know much more about fusion.