I've had a burning question for a long time, and I cannot seem to find reliable information through Google searches. If I get a PhD in let's say, Astrophysics, is it possible for me to switch to mathematical physics(in terms of career/research)? In general, I am uncertain how the academic system works for most doctorates. I get that a chemistry PhD probably cannot work in physics and vice-versa, but I am uncertain how important the specialty of a specific field is (in this case, physics). I would love to work in astrophysics (for the low pay post-docs and nonexistent jobs, yay!), but I also have a deep love of abstract and rigorous math. So my thinking is that mathematical physics might be a good fit for a PhD, but I still wouldn't mind working in Astrophysics or any of the almost innumerable fields of physics. So I'm curious if I can potentially work in accelerator physics with a nuclear physics degree, for example. I get that individuals with an actual PhD in that specific specialty probably will get a certain job over me, but I'd like to know if I would be automatically excluded from consideration. I am curious from the perspective of many different possible employment situations as well (academia, national lab, observatory, private industry, etc). Thanks for any help!