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Physics What do theoretical physicists actually do?

  1. Dec 27, 2017 #1
    Dear PF community,

    I was wondering, what do theoretical physicists actually do? Putting teaching and marking responsibilities aside, would you be able to describe to me your day-to-day activities when you do research? It is something that has been on my mind for a while.

    I suspect PF members will now ask me to elaborate on what I mean by “theoretical physicist”. What I mean is someone who is not engaged into experimental work (hence, I am not restricting the question solely to string theorists). Do you construct mathematical models to explain experimental results? What programs do you use? Do you use Matlab when doing computations? Or Mathematica perhaps? I read somewhere that exactly solvable problems in physics and maths are rare – does that mean you often use approximations or numerical analyses? How often do you collaborate with experimentalists in your research area? Etc.

    Thank you for reading so far, happy holidays everyone! :)
  2. jcsd
  3. Dec 27, 2017 #2

    Excellent question, I am still an undergrad but I have also asked the question many times, heres how an ordinary day can look like for my friends who does research, besides all teaching and responsibilities.

    They are usually a part of a research team (even though they might work very independently) doing research on a subject, not always to expect a specific solution/answer but sometimes just to deepen in a field.

    My friend do research beyond the standard model, he investigates and predicts how particles interact at very high energy levels.

    He reads articles related to his work to gain eventual insight. Sit with java or c+ to simulate a particle collision/interaction at very high energy levels, run some simulations and sit and analyze the result, was it expected, was something strange, why was it strange? And then do it again. This subject is very hard to do manual computations around so he mainly work with hes computer.

    He also skype and do meetings to discuss results, get input from other in the research-team or with research-teams in a similar area.

    Eventually he finds an interesting pattern in behavior/outcomes and write an article about it (actually parallell with the work).

    He fines it, and hope one day hes predictions will be found at cern.

    It is hard to map down a day because one never know the project will turn out, one answer open up the door to even more questions.

    I have other friends, phd-students, who only work with pen and paper to solve differential-equation problems, so they read, think, do math, discuss and write articles.
  4. Dec 27, 2017 #3
    Some of the more pure theorists will come along and give their answers which will provide a more complete picture, but I've published enough theory papers and worked with enough theorists in atomic physics to begin to paint a picture.

    Most of the theoretical physics I've seen and been a part of is developing and implementing theory to either make predictions for experiments that are expected in the next few years or to explain and validate new theoretical methods with recent experimental results. Since the calculations tend to be computationally intensive, they tend to be coded in C or Fortran rather than Matlab or MMA. Once a theoretical method and computational results are validated by comparison with experimental results, they can be used to more fully explore the parameter spaces and make predictions relating to system behavior in areas where experimental results are not yet available.
  5. Jan 16, 2018 #4
    Just one quick question - when you say C, do you mean any one from the whole family of languages: C/C++/C#, or are you referring to C specifically?

    Thank you both for your replies, FilipLand and Dr. Courtney. Sorry it took me so long to get back to it, I have been on holidays.
  6. Jan 16, 2018 #5

    Dr Transport

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  7. Jan 16, 2018 #6
    Most of what I've seen and done has been in C. I would not put a premium on learning other variants for number crunching. But it's possible you get dropped into a group where you need to roll with a variant.
  8. Jan 17, 2018 at 1:51 AM #7


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    From my experience most successful theorists work in close collaboration with one or several groups of experimentalists. You have to develop a thorough understanding in how these experiments work and be able to interpret the outcome or predict new experiments to confirm your hypotheses.
    Theoreticians work on all fields, not only particle physics, but from biophysics, solid state physics, nuclear physics to chemical physics.
    While it is true that a model which is realistic in all respects is often too complicated to be solved analytically, I think that finding analytical models which allow you to develop a qualitative understanding of what is going on is an important task of a theoretician.

    Most theoreticians prefer to use open code, often in c++ these days and at least partly written by themselves, to Matlab. Maple and Mathematica come very handy to do and plot analytical calculations.
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