<p>So grad school requires 3 letters of recommendation, blah blah blah, we know the drill.</p>
<p>Some preliminary info before we get started. I am a math student and I will be applying (for the 2nd time) to math phd programs this Winter. My statement of purpose portrays a strong intention to pursue geometry, mathematical physics and some dynamical systems (chaos, attractors).</p>
<p>OK, now that that is out of the way. I am currently planning on having 4 possible professors to ask for recommendations. One is a world famous math professor, another one is a very famous professor (IN HIS FIELD OF STUDY ONLY) that I will be finishing a paper with, another in a very famous physics professor (amongst physicists, he is very well known) that I am currently doing a reading on algebra and particle physics (from spin to unified field theories) and a very young (under 35 years old) math professor that I am working on a project in geometry and general relativity.</p>
<p>The first two professors are locks to get letters from, I think they will be good to really good letters. I am wondering who do I ask between the physics professor and the very young math professor?</p>
<p>The physics professor is a theoretical physicist, works in string theory, etc.</p>
<p>Ask both. How bad could it be to have 4 recommendations. Many of the schools I am applying to say something along the lines of 3 or more recommendations.</p>
<p>Where do these professors have professional and personal contacts?</p>
<p>Do they actually know you well, or are you just asking them because they are Dr. Famous, Dr. Almost-as-Famous, and Dr. Pretty-Famous?</p>
<p>Do the students they usually write letters for get into the programs that those students want to get into, and do they get funding?</p>
<p>When you say "I would like to apply to the Ph.D. in X at University Y, and I would like you to write one of my letters of recommendation, if you are willing do do so." what kind of response do you get?</p>
<p>If you ask "Who else do you think would be a good person for me to ask?" what kind of response do you get?</p>
<p>There is every chance that if you are interested in going to work with Dr. Very Young's old department, he/she is the best person for a letter to that university.</p>
<p>Wishing you much success in this endeavor.</p>
<p>I agree with belevitt...unless the application specifically says to send 3 and ONLY 3 (be careful, some do) it sounds like a fourth in your situation would not hurt you. A fourth letter from someone that knows you in exactly the same way as the other three adds nothing to an application, but these four people seem to be diverse enough that it cannot hurt.</p>
<p>Good to have a fourth in case someone flakes out at the last minute (like in my case.... that was NOT fun).</p>
<p>I think most of these online applications limit you to only 3 letters of recommendation. Most of the schools I will be applying to are Applyourself or embark sites, and I'm pretty sure these sites limit you to 3. I could be wrong though. I'm sure I could get my professors to just email the 4th letters. But I don't want to not follow the rules.</p>
<p>If I remember correctly Applyourself required 3 for submission, but allowed for more. But I could be wrong here.</p>
<p>Schools are more likely to get annoyed if you send in extraneous LORs from your pastor, your mom, your high school badminton coach. As long as they are relevant and diverse and add to your application, I don't see how an extra one would hurt. And as ticklemepink suggests, it may not hurt to have the reserve in case one flakes. I had to call one of my profs while he was on vacation to remind him that the letter was technically "due" in 20 minutes. He sent it later that night and all was well, but still...can get stressful.</p>