For the people who are in either of these fields, which math did you encounter most frequently in the field? Abstract Algebra, Analysis, Probability, Statistics, Calculus, or other? I have taken introductory courses for both topics at university and both seem to involve a wide range of math disciplines. I am pretty sure that I can't learn all of the branches of mathematics involved in quantum and stats mech. I would like to know which one I should focus on (and the reason why, if possible). Thank you in advance.