I'm about to head off to graduate school and (like many other physics students) I love theory, and especially GR, which is what my undergraduate research has been in. But, I'm also aware of the limitations on eventually finding a job. I'd eventually like to work. So, I've been tossing around the idea of leaning more towards gravitational wave physics than just pure gravity theory. However, I also love math (pure math) and am wondering - if I move to gravitational waves, will I have to say goodbye to my favorite mathematical objects (diffeomorphisms, groups, etc) forever? Because that would make me sad... I LOVE the math in GR; in fact, I'm pretty sure that's mostly why I love GR... any thoughts?