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I'm about to complete my PhD in mathematics. I've been working with Group theory (Representations). Besides the PhD I also did a master's in theoretical physics (I took much more courses than necessary to earn the degree and all of them were in advanced level, and did really well). The thing is: I would like to work in Theoretical Physics, and I'd like to use my Math background and apply it to theoretical physics. I love both subjects and I think they are like brothers in a sense. So my question is:
1) Should I apply for a second PhD (In physics)? For me it would be the worst option, since I'd have to spent a lot of time in things that I already know, and I don't see the point of writing another thesis. I heard that in Europe some universities "hire" PhD students as Research Assistants, so maybe this wouldn't be so bad. What you think?
2) Apply for a PostDoc position in theoretical physics? This is the best option in my opnion, but I don't know if physics departments welcomes mathematicians applying for PostDocs positions, Do they?
Observe that this question is not answered in another post, my question is specific to math/theoretical physics research. Besides I'm not thinking in getting a second PhD to "learn" physics, I am asking about what is more reasonable when considering to do research both in math and in physics.