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Page last updated 9/16/2024.

Advice for undergrads interested in doing theory in grad school

Question

What would you generally recommend students interested in theory do in undergraduate, to prepare best for the ultracompetitive theory graduate school admissions? Most students will not be able to even remotely get involved in High Energy theory/Cosmology until third year with advanced mechanics and quantum. Even then, most topics in modern HEP/Cosmo are locked behind GR and QFT, and potentially even String Theory which are not really taught in most undergraduate institutions bar the occasional Intro relativity class. What are some topics of theory research more accessible to undergraduates in this vein. Would participating in experimental HEP or observational cosmology provide similar benefits as compared to directly theory and should this be done? Would graduate schools be willing to take a theory student with almost no theory research in undergraduate and instead with experimental particle research or observational cosmology? Thanking you in advance and would greatly appreciate any advice.

Answer

In general, students interested in theory should take advanced physics courses, and preferably some math courses too, and do well in them. Ideally, they should also try to participate in some theory research during undergrad in order to get a taste of what they are signing themselves up for. At Cornell, this often translates to students taking QM earlier on so that they are prepared for QFT by their junior/senior year. GR is another course commonly taken by prospective theorists, and some students are ready to tackle it by their sophomore/junior year. Regardless of when you learn these subjects, make sure you are adequately prepared—the professors will not hold back on content and workload. As for more specialized courses like String Theory and QFT III, you do not need to worry about them unless your PI recommends you take them (and at Cornell, they are not always offered anyway). Besides, many theory projects begin with literature reviews, so you will learn the requisite material one way or another.

Now, what should a student who has not yet taken QFT/GR do in the meantime? The most common route is to participate in experimental research. This can be beneficial for surveying and contextualizing a research area to better appreciate the many different flavors of work being done; any good theorist should be aware of the experimental developments in their field. There is the possibility that you even will enjoy experimental work—you won’t know unless you try. It could also give you an opportunity early on to make significant research contributions and perhaps produce publishable work. That being said, knowledge gained from these labs will likely not directly translate to theoretical work, especially if you are doing a project that is very hands-on like building a telescope or some part of a particle accelerator.

Sometimes, knowledge of QM is sufficient to join some phenomenological particle physics and condensed matter theory groups. You may begin with a project that is a little less mathematical and more computational, then work up to a more mathematically rigorous project. Another research topic you could explore at Cornell is numerical relativity.

If you find it more worthwhile to spend time taking advanced classes and self-studying rather than doing experimental research, then that may be okay, as you should not force yourself to do experimental work just for the sake of doing it. There have been undergrads at Cornell who have gone directly into theory and have done well without having experience in experimental research. However, at an institution like Cornell, which does have many opportunities for underclassmen to do experimental research, it may not be a bad idea to try it. You can always leave a lab if you do not enjoy the research. Labs are usually understanding and have the expectation that undergrad research is more for the benefit of the undergrad than the group itself.

One caveat is that graduate school applications will require multiple professors to vouch for you. Students who only do theory research may not have as many research PIs who can speak on their behalf, as students often only join theory groups later on in their undergrad career. In this case, it can be a good idea to consider asking a professor who taught a class in which you did well. Given the emphasis on coursework and grades in theory graduate school applications, this may not be a bad idea even if you have multiple research PIs.

Another thing to keep in mind is that getting your foot in the door via experimental research early on can lead to other opportunities. Your PI can advocate for you when it comes to summer opportunities off campus (ex. REU programs), fellowship applications, and even contacting theory professors, which can give you a better chance at joining a theory group than just a cold email.

For your last question, it depends. If you have demonstrated a solid grasp of your coursework and have strong letters from your PIs, it is possible—however, you should make sure that theoretical research is something you truly want to do and clearly lay out your intentions when applying. If you attend an institution with opportunities for undergraduate theory research, then it is highly recommended that you join a group. Though there is a higher barrier to entry, careful planning earlier on and good performances in your courses (which is always helpful) should be sufficient, and most people who are serious about doing theory research are successful in joining groups. You can always reach out to theory professors to ask if they are taking students and what prerequisites there are to joining their groups; many professors are approachable and give useful advice.

Some parting thoughts: it’s great that you are thinking ahead about how to best prepare for this path. The expectations for theory grad school may feel daunting right now, but you will have plenty of time in undergrad to accomplish all of these things. Try out different research groups, talk to professors, and take advanced courses when you are prepared. Finally, try to enjoy your time in college too—the academics can be intense, but the exploration and growth you do outside the classroom can be just as exhilarating and rewarding. Wishing you the best.