I think the kind of mathematical problem solving we’re engaged in is common across theoretical physics (although this is just my impression as a non-physicist). I’ve noticed that some specific topics that have come up (such as Gaussian integrals and permanents) also crop up in quantum field theory, but I don’t think that’s a strong reason to prefer that background particularly. Broad areas that often come up include probability theory, computational complexity and discrete math, but it’s not necessary to have a lot of experience in those areas, only to be able to pick things up from them as needed.
I think the kind of mathematical problem solving we’re engaged in is common across theoretical physics (although this is just my impression as a non-physicist). I’ve noticed that some specific topics that have come up (such as Gaussian integrals and permanents) also crop up in quantum field theory, but I don’t think that’s a strong reason to prefer that background particularly. Broad areas that often come up include probability theory, computational complexity and discrete math, but it’s not necessary to have a lot of experience in those areas, only to be able to pick things up from them as needed.