Is there a good way to apply to graduate schools with an undecided research focus? I'm not completely undecided; I'm definitely leaning towards certain things (theory/mathematical, particle, medical, fluids) and away from others (experimental, solid-state), but I don't think I'm ready to say "I want to spend 6 years in graduate school studying _________". I'm also not sure if I can safely rule anything out either (except for solid-state).
Anybody have any advice on applying with an unspecified research focus? Anybody care to share how they decided on a particular subfield?