She has a PhD in category theory. >Category Theory doesn’t deal with number theory all that much. Not sure where you are drawing the line here since algebraic

She has a PhD in category theory. >Category Theory doesn’t deal with number theory all that much. Not sure where you are drawing the line here since algebraic geometry (aka modern number theory) makes extensive and extremely deep use of category theory. Ravi Vakil’s Rising Sea being the best intro to this point of view. This example is just a fun way to talk about posets.