I'm looking to apply to physics departments that have the best combination of research in theoretical particle physics, mathematical physics, and gravitational physics (also theoretical) - or at least the first two out of these three. I'm especially looking for ones that have particle physics faculty with joint math department appointments and/or that allow grad students to pursue research in both departments (i.e. with one advisor in phys, the other in math).

What are the opinions and suggestions out there?