What impact does a potential advisor have in Phd admissions?

Question

Sorry if this question has been asked before.

I recently reached out to the advisor I want to do my PhD with. This is a person that I have corresponded with in the past (I wanted to collaborate with her back when I was an undergrad but she was going on sabbatical and was unavailable). She responded quickly, and I ended up meeting with her where she briefly interviewed me about my experience and then she gave me a tour of her lab and introduced me to some of her current students.

Additionally, one of my letters of recommendation was written by a close friend of hers who does research in the same field. Recently I was catching up with this person and they told me that the potential advisor I met with was "excited to have" me join their group. However, when I toured her lab she told me she was glad I was passionate about their research but that she was "not on the admissions committee".

What impact does this potential advisor have on my admissions decision if she's not a member of the committee? Will the committee take her thoughts into account, even if, for instance, the committee itself found me less desirable for the university?

Answer 1

There is no single system in the US, so every department can manage their admissions process however they want.

In the arrangement I am most familiar with, the limiting factor on the number of admitted students is money ("money" could be based on "number of TA slots", or traineeship/fellowship slots). The primary criteria for admission are potential and fit. So, you rank the students by some rough weighted combination of potential and fit, and admit from the top to the bottom of the list until you run out of money.

Potential is how "good" a student is - how likely they are to succeed in the program and in the future. A potential future advisor doesn't have much influence on potential - potential is better judged by people the student has worked with in the past, not the future.

Fit is about how well the student matches the particular program: if a student really wants to study an area of physics that no one at the university studies, maybe that student has a lot of potential but they're a poor fit. Interest between a potential advisor and a student counts positively towards fit, even if the advisor isn't on the admissions committee.

Money is something that a potential advisor can influence most directly. Note that the process "rank students and admit until you run out of money" doesn't mean that every qualified student is admitted. If a student is below the program's "money threshold", they might still be able to accept a qualified student who has funding available separate from the department's own money pool. That could be an outside fellowship, or a promise of funding support from a faculty member, contingent on the student joining that person's lab. However, if your intended area of study is not one where there is sufficient grant money given to professors for them to fund students directly, this may not be an option for your specific case; I'd expect it would have been mentioned directly as an option if it were.

Answer 2

In the US it is unlikely that, in your case, a potential advisor will have any influence, or even any interest in influencing the decision at this point in time.

Some fields in physics (high energy, perhaps) where people need vast funding and extensive labs, might be different, but for the most part, the doctoral program will be course intensive at the start, leading to the comprehensive exams. Once you get through those, you can get serious about a research advisor.

But generally, the advisor isn't the one responsible for your funding (the department is) and so will wait to take on students until they are "ripe".

If you are in an exceptional case (or in Europe) then the conversation has already discussed funding, I'd expect.

The advisor might already be on the admissions committee or, in an exceptional case (truly exceptional - young Dirac/Einstein) might put in a word, but admissions is normally done on a wide range of factors as indicated by the extensive admissions materials.

My best guess is that they will have little impact either way unless they already want to fund you, which is more likely to happen later. Telling you that they aren't on the committee, however, is a strong indicator that they won't be involved.

The people who write letters of recommendation for you probably will have more influence on the committee, assuming they confidently predict your success.

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See: How does the admissions process work for Ph.D. programs in Country X?