Is there a field of "Mathematical Astrophysics"? Just was wondering (for graduate school purposes), is there a field that does what mathematical physics does but for astrophysics? (e.g., perhaps simplifying or re-expressing the mathematics used in some subdiscipline of astrophysics?) Or perhaps there is something similar to that? At the (few) research programs I've looked at in graduate schools, it seems "mathematical physics" tends to be associated with quantum and string stuff.