I believe the general research areas/specialties of each of the main scientists in The Big Bang Theory are well known to viewers, as follows:
- Sheldon: theoretical physics
- Leonard: experimental physics
- Raj: astrophysics
- Howard: mechanical/electrical engineering
(but I count him as a scientist for this question because it's easy)
- Amy: neuroscience
- Bernadette: microbiology
How much more precisely can we identify the specific subfields they work in? What evidence exists in the show that one would use to make such an identification?
Of course, I'm aware that if one looks too closely, the evidence will be inconsistent, e.g. Sheldon usually works on string theory and particle physics but spends a whole episode on the motion of electrons through a crystal lattice, which is only vaguely related. But I'm willing to excuse an occasional diversion into a different research topic (which is plausible). I would imagine the majority of each character's work in the show centers around some topic which can be identified more specifically than just e.g. "experimental physics," and that's what I'm curious to know about.