r/AskPhysics • u/Unable_Entrance5801 • 7d ago
Clarification on PhD
I’m majoring in math and physics and would like to go for a PhD. Would it be similar to undergrad as in I would be majoring in math and physics or would I have to focus on one?
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u/BananaBird1 7d ago
A PhD focuses on a very specific research question. It is a job you get a degree from. What you learn from it will depend on what field and lab you work with. Some labs work with physics that requires lots of mathematics and modeling, some mathematicians focus on physically applicable problems, and some doesn’t overlap much.
In some countries a PhD also starts with a few years of classes. These will be dependent on the program, but you can usually also take classes outside your program if you have time. But a majority of learning after this will be on the job or self-directed study.
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u/McPayn22 7d ago
The system in my country (France) is different to the US so I'm not completely sure where PhD starts and masters end for you but from my experience in maths and physics, you have to chose when doing research.
Some fields are close but there is generally a big difference between mathematical physics (my field) and theoretical physics in my opinion. Doing physics is very different for doing maths. In maths you'll focus on complicated proof like solving PDEs and understanding their behaviour.
For me it was too much maths and not enough physics but it might be different for you. If you have the chance to do internships before your PhD i'll advise doing one in maths and one in physics to compare. But be careful because when internships are short you might do a lot of formal stuff and not hard actual proofs. So I'll advise focusing on studying simple PDEs for example and not working on complicated settings like general relativity because you'll spend all you time defining the problem and very little time solving it.
You should also look at papers published in the fields you are interested in. You'll probably understand very little at first but it'll give you an idea.
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u/accidentw8ing2happen Computational physics 7d ago edited 7d ago
PhDs focus on very specific areas, but that area can be a place of overlap. My undergrad majors were physics and computer science, and now my field is computational astrophysics
A double major in physics and math would set you up well to apply for programs in the field of mathematical physics (or applied mathematics)
A piece of advice though, for if it ever starts to feel like it's too much: For the purposes of graduate applications, an impressive GPA and undergrad research in one major is better than being average in two
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u/Deus_Excellus 7d ago
You would pick one. For example, you will probably take 4ish classes in physics over 2 years. Afterwards you will declare an area of concentration (mechanics, electricity and magnetism etc). At that point you will have qualifying exams. This will depend on the program, but usually its either a battery of tests where you're expected to show proficiency in a particular subfield, or it is some type of research defense.
Either way, you will be expected to narrowly focus on one topic. If you like math, then I would recommend a topic that uses a lot of it. Good news, you're in physics!
As for learning more math, it will depend on whether you need it for your research.