It seems like there is no specific Theoretical Physics major. You can major in Astrophysics, Biophysics, Chemical Physics, Engineering Physics, and just plain Physics. At the master/doctorate level you have to specialize in astrophysics, biophysics, chemical physics, geophysics, material science, nuclear physics, optics, particle physics, or plasma physics. Theoretical Physics isn't listed as a particular field. Can you jump into theoretical physics from any physics discipline (such as astrophysics or particle physics)? And theoretical physicist are employed mainly by universities, correct?