For starts, I'm a math major and physics minor.
TLDR:
I'm applying to math graduate schools. Should I submit a letter of recommendation from a physics professor?
Longer version:
I'm applying to math graduate schools. More specifically, I'm applying to math programs that do research in the realm of mathematical physics (e.g., string theory & algebraic geometric, TQFT, ect.). As typical, every school I'm applying to wants three letters of recommendation (LOR). I currently have two strong LORs from math professors. I could get a third LOR from math professors, but admittedly it will not be strong (i.e., it would be the standard "he made an A", "was a good student", and since I wrote lecture notes for the course they would perhaps mention this).
On the other hand, I took a physics course (Lagrange mechanics), and always scored around 40 points higher than the class average. The professor commented on my scores a number of times. So, I'm curious, would it be worth submitting a LOR from this physics professor, or should I just get another LOC from a math professor? Also, it seems to make sense to show the graduate schools I do well in physics, since I'm interested in mathematical physics.