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Is a physicist limited by their chosen PhD?

  1. Jan 24, 2015 #1
    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!
  2. jcsd
  3. Jan 24, 2015 #2
    In addition, is it possible to simply earn a physics PhD, instead of a specific field like "solid-state physics"?
  4. Jan 24, 2015 #3

    Vanadium 50

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    One's PhD is, at least in the US, usually designated only by department - for example, mine say "Doctor of Philosophy, as recommended by the Department of Physics". However, your dissertation is in some subfield, and that's where your expertise will lie. If you studied, say, theoretical nuclear physics, and there was a position open for an expert on experimental thin films, there is nothing precluding you from applying, but that doesn't mean you will be the most qualified candidate.
  5. Jan 24, 2015 #4
    So it is primarily about what your main thesis was regarding? What if you have publications in other areas, would that increase your visibility in those respective fields? Granted, it would probably be difficult to engage research in multiple sub-fields while pursuing a PhD.
  6. Jan 24, 2015 #5


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    I received my PhD in experimental condensed matter physics, and I later on switched field and went into Accelerator Physics.

    I have seen a lot of people who received their degree/Phds in one area, and went on to do well in other areas.

    You need to keep in mind that, especially in experimental work, your "expertise" covers a wide area of applicability. Just because I made thin films of superconductors to study its tunneling spectroscopy doesn't mean that the skills that I acquired in producing those thin films are only limited to making superconductors. I can use that skill to fabricate all kinds of films and material. It is why I strongly emphasize students learn a lot of skills during their academic years. These skills often go beyond just the narrow confines of one's area of study!

  7. Jan 24, 2015 #6


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    Most people find it hard enough to gain expertise in one subfield while finishing their Ph.D., let alone two.

    After you have established yourself somewhere, it is possible to branch out or shift over to a different field. While I was finishing my Ph.D. in experimental particle physics, my advisor started to shift over to biophysics by spending part of his time working with a colleague in our department. As the experiment that we had been working on wound down (after I left), he spent more time doing biophysics, and eventually ended up doing that exclusively.
  8. Jan 24, 2015 #7
    This is actually a great example, because I've read that employment in Accelerator Physics is in high demand, unlike Astrophysics. I'd rather do something physics related than a field that is completely unrelated.
  9. Jan 24, 2015 #8
    By establish yourself, do you mean doing postdoctoral positions for some time? Probably producing publications as well, I'm guessing.
  10. Jan 24, 2015 #9
    It's definitely possible, but not easy. I know of someone who did a PhD in theoretical physics, in string theory, and then went on to do post-docs in condensed matter experiment.

    Maybe this student started out in CME and switched to string theory so he/or she may have had past experience? Anyways I think if you highlight your skill set well enough you can certainly apply for positions outside of your subfield.
  11. Jan 24, 2015 #10

    Vanadium 50

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    Zz's experience is worth looking at - to move subfields, two things needed to happen: it had to be a subfield that had room, and he had to have learned something relevant to the new field, like the ability to make photocathodes. This is a very different thing that getting a PhD in formal, mathematical theory and then trying to find a job in a crowded field.

    And you won't have the time or the ability to publish in multiple subfields when pursuing a PhD. It will be plenty of work with just one subfield.
  12. Jan 24, 2015 #11
    Well, I thank all of you for your advice and input. Truthfully, I'm still an undergrad, so it is pretty early to worry about this kinda of stuff. In the end, I'll probably go with what excites me and say to hell with the consequences. I am taking some engineering classes as well though, to give myself the possibility of either double major in physics/engineering or double major in math/physics, earn a master's in engineering and then earn a doctorate in some sub-field of physics I enjoy (I think that's feasible based on what I've read). I do know one non-physics career I wouldn't mind working in though. I've heard that companies like Google often hire people with math heavy backgrounds to code. I wouldn't mind being a code monkey (although Microsoft is the embodiment of all that is evil). Starting next semester, I plan on taking a few extra CS courses to get some formal CS theory. Unfortunately, I don't think I could ever work in finance (I have a theft record from when I was a stupid kid), but I never was interested in finance anyways. One class of economics was enough to squash any chance of being interested in social sciences.
  13. Jan 27, 2015 #12
    I don't know if jobs in accelerator physics are in high demand compared to astrophysics, but there aren't a whole lot of jobs in the field desperate to be filled or anything like that. However, if you get in to the right school for graduate work (that is associated with a national lab, usually) there is some interesting mathematics involved in accelerator physics, like non-linear motion. There are a few guys that come to mind who's work is very mathematically oriented, so that might be possible.
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